MediaWiki:Manual of Style

The Manual of Style, often abbreviated MoS, is a style guide for users that aims to make the encyclopedia easier to read. One way of presenting information is often just as good as another, but consistency promotes professionalism, simplicity and greater cohesion in Wikipedia articles. An overriding principle is that style and formatting should be applied consistently throughout an article, unless there is a good reason to do otherwise (except in direct quotations, where the original text is generally preserved).

If the Manual of Style does not specify a preferred usage, discuss your issues on the talk page of this manual. The menu to the right contains links to Manual of Style pages that explore topics in greater detail.

When either of two styles is acceptable, it is inappropriate for an editor to change an article from one style to another unless there is a substantial reason to do so (for example, it is acceptable to change from American to British spelling if the article concerns a British topic). Edit warring over optional styles is unacceptable. If an article has been stable in a given style, it should not be converted without a reason that goes beyond mere choice of style. When it is unclear whether an article has been stable, defer to the style used by the first major contributor.

Article titles, headings and sections

Article titles

Article titles generally comprise nouns or noun phrases.

Effects of the wild, not About the effects of the wild

The title should be short—preferably fewer than ten words.
Only the first letter of the first word, letters in acronyms, and the first letter of proper nouns are capitalized; all other letters are in lower case.

Funding of UNESCO projects, not Funding of UNESCO Projects

Unless part of a proper noun, a, an and the are normally avoided as the first word

Economy of the second empire, not The economy of the second empire

Pronouns (you, they) are normally avoided, except when they form part of the title of a work.
Links are never used, in favor of linking the first occurrence of the item in the text.
Special characters such as the slash (/), plus sign (+), curly brackets ({ }) and square brackets ([ ]) are avoided; the ampersand (&) is replaced by and, unless it is part of a formal name.

Note: This guidance also applies to Section headings below.

First sentences

If possible, an article title is the subject of the first sentence of the article; for example, "The Manual of Style is a style guide" instead of "This style guide is known as ...". If the article title is an important term, it appears as early as possible. The first (and only the first) appearance of the title is in boldface, including its abbreviation in parentheses, if given. Equivalent names may follow, and may or may not be in boldface. Highlighted items are not linked, and boldface is not used subsequently in the first paragraph. For example: "Vienna (Template:Lang-de Template:IPA, see also its other names) is the capital of Austria and one of that country's nine states."
If the topic of an article has no name and the title is merely descriptive—such as Electrical characteristics of a dynamic loudspeaker—the title does not need to appear verbatim in the main text; if it does, it is not in boldface.
The normal rules for italics are followed in choosing whether to put part or all of the title in italics ("Tattoo You is an album by The Rolling Stones, released in 1981").

Section headings

Template:Shortcut Note: The guidance in Article titles above also applies to section headings.

Unspaced multiple equal signs are the style markup for headings. The triple apostrophes ( ''' ) that make words appear in boldface are not used in headings. Nest headings correctly. The hierarchy is as follows:
- the automatically generated top-level heading of a page is H1, which gives the article title;
- primary headings are then ==H2==, followed by ===H3===, ====H4====, and so on.
Spaces between the == and the heading text are optional (==H2== versus == H2 ==). These extra spaces will not affect the appearance of the heading, except in the edit box.
Spaces above and below headings are optional. Only two or more line-spaces above and below will change the appearance by adding more white space.
Avoid restating or directly referring to the topic or to wording on a higher level in the hierarchy (Early life, not His early life).

Section management

Headings provide an overview in the table of contents and allow readers to navigate through the text more easily.
Change a heading only after careful consideration, because this will break section links to it from the same and other articles. If changing a heading, try to locate and fix broken links; for example, searching for wikipedia "section management" will probably yield links to the current section.
When linking to a section, leave an editor's note to remind others that the title is linked. List the names of the linking articles, so that if the title is altered, others can fix the links more easily. For example: ==Evolutionary implications== . Italicize the section name only if it otherwise requires italics (such as the title of a book). Linking a term provides sufficient indication that you are using a term as a term, which requires italics.
When referring to a section without linking, italicize the section name; for example, the current section is called Section management.
The standard order for optional appendix sections at the end of an article is See also, Notes (or Footnotes), References, Further reading (or Bibliography), and External links; the order of Notes and References can be reversed. See also is an exception to the point above that wording comprises nouns and noun phrases. For information on these optional sections, see Wikipedia:Guide to layout#Standard appendices and descriptions and Wikipedia:Citing sources.

Capital letters

Main article: Wikipedia:Manual of Style (capital letters)

There are differences between the major varieties of English in the use of capitals (uppercase letters). Where this is an issue, the rules of the cultural and linguistic context apply. As for spelling, consistency is maintained within an article.

Within articles and other wiki pages, capitals are not used for emphasis. Where wording cannot provide the emphasis, italics are used.

Incorrect:	Contrary to popular belief, aardvarks are Not the same as anteaters.
Incorrect:	Contrary to popular belief, aardvarks are NOT the same as anteaters.
Correct:	Contrary to popular belief, aardvarks are not the same as anteaters.

Titles

When used as titles (that is, followed by a name), items such as president, king and emperor start with a capital letter: President Clinton, not president Clinton. The formal name of an office is treated as a proper noun: Hirohito was Emperor of Japan and Louis XVI was King of France (where King of France is a title). Royal styles are capitalized: Her Majesty and His Highness; exceptions may apply for particular offices.
When used generically, such items are in lower case: De Gaulle was a French president and Louis XVI was a French king. Similarly, Three prime ministers attended the conference, but, The British Prime Minister is Gordon Brown.
For the use of titles and honorifics in biographical articles, see Honorific prefixes.

Religions, deities, philosophies, doctrines and their adherents

Religions, sects and churches and their followers (in noun or adjective form) start with a capital letter. Generally the is not capitalized before such names (the Shī‘a, not The Shī‘a). (But see also the style guide and naming convention for the Latter Day Saint movement.)
Scriptures are capitalized but not italicized (for example, the names of the Qurʾan, the Talmud, the Granth Sahib, and the Bible). When the is used, it is not capitalized. Some derived adjectives are capitalized by convention, some are not (biblical, but normally Koranic); for others, check a dictionary appropriate to the topic, and be consistent in an article.
Honorifics for deities, when used alone in reference to a specific figure of veneration, start with a capital letter (God, Allah, the Lord, the Supreme Being, the Great Spirit); the is not capitalized. The same is true when referring to major religious figures and figures from mythology by titles or terms of respect (the Prophet, the Messiah, the Virgin, a Muse). When used generically, descriptively or metaphorically, such descriptive terms are not capitalized; thus the Romans worshipped many gods, many Anglo-Saxons worshipped the god Wotan, Jesus and Muhammad are both considered prophets in Islam, biblical scholars dispute whether Mary was a virgin for her entire life, and her husband was her muse.
Pronouns and possessives referring to figures of veneration are not capitalized in Wikipedia articles, even when they traditionally are in a religion's scriptures. They are left capitalized when directly quoting scriptures or any other texts that capitalize them.
Broad categories of mythical or legendary creatures do not start with capital letters (elf, fairy, nymph, unicorn, angel), although in derived works of fantasy, such as the novels of J.R.R. Tolkien and realtime strategy video games, initial capitals are sometimes used to indicate that the beings are regarded as cultures or races in their fictional universes. Names or titles of individual creatures are capitalized (the Minotaur, the Pegasus) as are those of groups whose name and membership are fixed (the Cherubim, the Magi or the Three Wise Men). As with terms for deities, generalized references are not capitalized (cherub-like, the priests of this sect were called magi by some, several wise men were consulted).
Spiritual or religious events are likewise capitalized only when they are terms referring to specific incidents or periods (the Great Flood, the Exodus, but annual flooding or an exodus of refugees).
Philosophies, theories and doctrines do not begin with a capital letter unless the name derives from a proper noun (capitalism versus Marxism) or has become a proper noun (lowercase republican refers to a system of political thought; uppercase Republican refers to one of several specific political parties or ideologies, such as the US Republican Party or Irish Republicanism). Physical and natural laws and parodies of them are capitalized (the Second Law of Thermodynamics, the Theory of Special Relativity, Murphy's Law; but an expert on gravity and relativity, thermodynamic properties, Murphy's famous mock-law). Doctrinal topics or canonical religious ideas (as distinguished from specific events) that may be traditionally capitalized within a faith are given in lower case in Wikipedia, such as virgin birth, original sin or transubstantiation.
Platonic or transcendent ideals are capitalized (Good, Truth), but only within the context of philosophical doctrine; used more broadly, they are lower-case (Superman represents American ideals of truth and justice). Personifications represented in art, such as a statue of the figure Justice, are capitalized.

Calendar items

Months, days and holidays start with a capital letter: June, Monday, the Fourth of July (when referring to the U.S. Independence Day, otherwise July 4 or 4 July).
Seasons, in almost all instances, are lowercase: This summer was very hot; The winter solstice occurs about December 22; I've got spring fever. When personified, season names may function as proper nouns, and they should then be capitalized: I think Spring is showing her colors; Old Man Winter.

Animals, plants, and other organisms

Main article: Wikipedia:WikiProject Tree of Life#Article titles

Scientific names for genera and species are italicized, with a capital initial letter for the genus but no capital for the species; for more specific guidelines for article titles, see Wikipedia:WikiProject Tree of Life#Article titles. For example, the tulip tree is Liriodendron tulipifera, and humans are Homo sapiens. Taxonomic groups higher than genus are given with an initial capital and are not in italics; for example, gulls are in the family Laridae, and we are in the family Hominidae.

Common (vernacular) names of flora and fauna should be written in lower case—for example, oak or lion. There are a limited number of exceptions to this:

Where the name is the first word of the sentence, it should be capitalized as any other word would be. For example, Black bears eat white suckers and blueberries.
Where the common name contains a proper noun, such as the name of a person or place, that proper noun should be capitalized; for example, The Amur tiger may have a range of over 500 square kilometers, or The Roosevelt elk is a subspecies of Cervus canadensis.
For specific groups of organisms, there are specific rules of capitalization based on current and historic usage among those who study the organisms. These should ordinarily be followed:
- Official common names of birds are normally capitalized
In a very few cases, a set of officially established common names are recognised only within a country or a geographic region. Those common names may be capitalized according to local custom but it should be understood that not all editors will have access to the references needed to support these names; in such cases, using the general recommendation is also acceptable.

In any case, a redirect from an alternative capitalization should be created where it is used in an article title.

Celestial bodies

Sun, earth and moon are not capitalized generally (The sun was peeking over the mountain top). They may be proper nouns in an astronomical context but only when referring to specific celestial bodies (our Sun, Earth and Moon): so The Moon orbits the Earth, but Jupiter's moon Io.
Other planets and stars are proper nouns and start with a capital letter: The planet Mars can be seen tonight in the constellation Gemini, near the star Pollux. Where a name has multiple words, it is treated like other proper nouns where each leading letter is capitalized: Alpha Centauri and not Alpha centauri.

Directions and regions

Directions such as north are not proper nouns and are therefore lowercase. The same is true for their related forms: someone might call a road that leads north a northern road, compared with the Great North Road. Composite directions may or may not be hyphenated (northeast and north-east, Southeast Asia and South-East Asia), depending on the general style adopted in the article.
Regions that are proper nouns, including widely known expressions such as Southern California, start with a capital letter. Follow the same convention for related forms: a person from the Southern United States is a Southerner. Regions of uncertain proper-noun status are assumed not to have attained it.

Institutions

Proper names of institutions (for example, the University of Sydney, New York-Presbyterian Hospital, George Brown College) are proper nouns and require capitalization. Where a title starts with the, it typically starts with lowercase t when the title occurs in the middle of a sentence: a degree from the University of Sydney.
Generic words for institutions (university, college, hospital, high school) require no capitalization:

Incorrect	(generic):	The University offers programs in arts and sciences.
Correct	(generic):	The university offers ...
Correct	(title):	The University of Ottawa offers ...

Acronyms and abbreviations

Main article: Wikipedia:Manual of Style (abbreviations)

See also "Latin abbreviations", below.

Write out both the full version and the abbreviation at first occurrence: Readers are not necessarily familiar with any particular acronym such as NASA (pronounced as a word) or initialism such as PBS (pronounced by saying the letters themselves). The standard practice is to name the item in full on its first occurrence, followed by the abbreviation in parentheses. For example, The New Democratic Party (NDP) won the 1990 Ontario election with a significant majority (first mention of New Democratic Party in the article) and The NDP quickly became unpopular with the voters (subsequent mention).; Initial capitals are not used in the full name of an item just because capitals are used in the abbreviation.

Incorrect	(not a name):	We used Digital Scanning (DS) technology
Correct:		We used digital scanning (DS) technology
Correct	(name):	produced by the British Broadcasting Corporation (BBC)

If the full term is already in parentheses, use a comma and or to indicate the acronym; for example, They first debated the issue in 1992 (at a convention of the New Democratic Party, or NDP).

Plural and possessive forms

Acronyms and initialisms are pluralized by adding -s or -es as with any other nouns (They produced three CD-ROMs in the first year; The laptops were produced with three different BIOSes in 2006). As with other nouns, no apostrophe is used unless the form is a possessive.

Periods and spaces

Acronyms and initialisms are generally not separated by full stops (periods) or blank spaces (GNP, NORAD, OBE, GmbH); many periods and spaces that were traditionally required have now dropped out of usage (PhD is preferred over Ph.D. and Ph. D.).

Truncated (Hon. for Honorable), compressed (cmte. for committee) and contracted (Dr. for Doctor) abbreviations may or may not be closed with a period. A period is much more usual in American usage (Dr. Smith of 42 St. Joseph St.); and no period is commonly preferred in British and other usage (Dr Smith of 42 St Joseph St, though one or other "St" might take a period, in such a case). Some British and other authorities prefer to drop the period from truncated and compressed abbreviations generally (XYZ Corp, ABC Ltd), a practice also favored in science writing. Regardless of punctuation, such abbreviations are spaced if multi-word (op. cit. or op cit, not op.cit. or opcit).

US and U.S.: In American English, both US and, decreasingly, U.S. are common abbreviations for United States; US is yet more common in other varieties. When referring to the country in a longer abbreviation (USA, USN, USAF), periods are not used. When the United States is mentioned along with one or more other countries in the same sentence, US or U.S. can be too informal, and many editors avoid it especially at first mention of the country (France and the United States, not France and the US). When the United States is mentioned by acronym in the same article as other abbreviated country names, for consistency do not use periods (the US, the UK and the PRC); and especially do not add periods to the other acronyms, as in the U.S., the U.K. and the P.R.C.). The spaced U. S. is never used, nor is the archaic U.S. of A., except in quoted materials. USA and U.S.A. are not used unless quoted or part of a proper name (Team USA).

In all of these matters, maintain consistency within an article. The sole exception is that for units of measurement, periods are not used even if other acronyms are dotted. (See Wikipedia:Manual of Style (dates and numbers) for more information.)

Do not use unwarranted abbreviations

The use of abbreviations should be avoided when they would be confusing to the reader, interrupt the flow, or appear informal or lazy. For example, approx. for approximate[ly] should not be used in most articles, although it may be useful in reducing the width of a table of data, and infobox, or in a technical passage in which the term occurs many times.

See also Wikipedia:Manual of Style (dates and numbers) for when to abbreviate units of measurement.

Do not invent abbreviations: Generally avoid the making up of new abbreviations, especially acronyms. For example, while it is reasonable to provide World Union of Billiards as a translation of Union Mondiale de Billard, the former is not the organization's name, and it does not use the acronym WUB; when referring to it in short form, use the official abbreviation UMB. In a wide table of international economic data, it might be desirable to abbreviate a United States gross national product heading; this might be done with the widely recognized initialisms US and GNP spaced together, with a link to appropriate articles, if it is not already explained: US GNP, rather than the made-up acronym USGNP.
HTML elements: The software that Wikipedia runs on does not support HTML abbreviation elements (<acronym> or <abbr>); therefore, these tags are not inserted into the source (see Mediazilla:671).

Italics

Template:Further

Emphasis: Italics are used sparingly to emphasize words in sentences (bolding is normally not used at all for this purpose). Generally, the more highlighting in an article, the less the effect of each instance.
Titles: Main article: Wikipedia:Manual of Style (titles)

Italics are used for the titles of works of literature and art, such as books, paintings and musical albums. The titles of articles, chapters, songs and other short works are not italicized, but are enclosed in double quotation marks.; Italics are not used for major revered religious works (for example the Bible, the Koran, and the Talmud).
Words as words: Italics are used when mentioning a word or letter (see Use–mention distinction) or a string of words up to a full sentence: "The term panning is derived from panorama, a word coined in 1787"; "The most commonly used letter in English is e". For a whole sentence, quotation marks may be used instead, as they are in this manual of style where this helps to make things clear: "The preposition in She sat on the chair is on", or "The preposition in 'She sat on the chair' is on". Mentioning (to discuss such features as grammar, wording and punctuation) is different from quoting (in which something is usually expressed on behalf of a quoted source).
Quotations in italics: For quotations, use only quotation marks (for short quotations) or block quoting (for long ones), not italics. (See Quotations below.) This means that (1) a quotation is not italicized inside quotation marks or a block quote just because it is a quotation, and (2) italicization is not used as a substitute for proper quotation formatting.
Italics within quotations: Italics are used within quotations if they are already in the source material, or are added by Wikipedia to give emphasis to some words. If the latter, an editorial note "[emphasis added]" should appear at the end of the quotation ("Now cracks a noble heart. Good night sweet prince: And flights of angels sing thee to thy rest" [emphasis added]).; If the source uses italics for emphasis, and it is desirable to stress that Wikipedia has not added the italics, the editorial note "[emphasis in original]" should appear after the quote.
Effect on nearby punctuation: Italicization is restricted to what should properly be affected by italics, and not the punctuation that is part of the surrounding sentence.

Incorrect:	What are we to make of that?
Correct:	What are we to make of that?
		(The question mark applies to the whole sentence, not just to that.)
Correct:	Four of Patrick White's most famous novels are A Fringe of Leaves, The Aunt's Story, Voss and The Tree of Man.
		(The commas, period, and and are not italicized.)

Italicized links: The italics markup must be outside the link markup, or the link will not work; however, internal italicization can be used in piped links.

Incorrect:	The opera [[''Turandot'']] is his best.
Correct:	The opera ''[[Turandot]]'' is his best.
Correct:	The [[USS Adder (SS-3)\|USS ''Adder'' (SS-3)]] was a submarine.

Non-breaking spaces

In compound items in which numerical and non-numerical elements are separated by a space, a non-breaking space (or hard space) is recommended to avoid the displacement of those elements at the end of a line.
A non-breaking space can be produced with the HTML code   instead of the space bar; thus, 19 kg yields a non-breaking 19 kg.


A non-breaking space can also be produced by using the {{nowrap}} template; thus, {{nowrap|8 sq ft}} produces a non-breaking Template:Nowrap. This is especially useful for short constructions requiring two or more non-breaking spaces, as in the preceding example.
In some older browsers, quotation marks separated by a non-breaking space may still be broken at the end of a line: ("She said 'Yes!' ").
Unlike normal spaces, multiple non-breaking spaces are not compressed by browsers into a single space.

Quotations

Template:Shortcut

See also Italics above, and Punctuation: Quotation marks below.
Minimal change
Wherever reasonable, preserve the original style and spelling of the text. Where there is a good reason not to do so, insert an editorial explanation of the changes, usually within square brackets (e.g., [for example]).
Attribution
The author of a quote of a full sentence or more is named; this is done in the main text and not in a footnote. An exception is that attribution is unnecessary for well-known quotations (e.g., from Shakespeare) and those from the subject of the article or section.
Quotations within quotations
When a quotation includes another quotation (and so on), start with double-quotes outermost and working inward, alternate single-quotes with double-quotes. For example, the following three-level quotation: "She disputed his statement that 'Voltaire never said "I disapprove of what you say, but I will defend to the death your right to say it." ' " Adjacent quote marks, as at the end of this example, are separated by a non-breaking space (&nbsp;), though this may not work on some older browsers.
Linking
Unless there is a good reason to do so, Wikipedia avoids linking from within quotes, which may clutter the quotation, violate the principle of leaving quotations unchanged, and mislead or confuse the reader.
Block quotations
A long quote (more than four lines, or consisting of more than one paragraph, regardless of number of lines) is formatted as a block quotation, which Wikimedia's software will indent from both margins. Block quotes are not enclosed in quotation marks (especially including decorative ones such as those provided by the {{cquote}} template, used only for "call-outs", which are generally not appropriate in Wikipedia articles). Use a pair of <blockquote>...</blockquote> HTML tags.  Note: The current version of Wikipedia's MediaWiki software will not render multiple paragraphs inside a <blockquote> simply by spacing the paragraphs apart with blank lines.  A workaround is to enclose each of the block-quoted paragraphs in its own <p>...</p> element.

Example:


<blockquote>

<p>And bring us a lot of horilka, but not of that fancy kind with raisins, or with any other such things—bring us horilka of the purest kind, give us that demon drink that makes us merry, playful and wild!</p>



<p>—''[[Taras Bulba]]'', by [[Nikolai Gogol]]</p>

</blockquote>

The result appears indented on both sides (and, depending on browser software, may also be in a smaller font):


And bring us a lot of horilka, but not of that fancy kind with raisins, or with any other such things—bring us horilka of the purest kind, give us that demon drink that makes us merry, playful and wild!
—Nikolai Gogol, Taras Bulba

The {{quote}} template provides the same semantic HTML formatting, as well as a workaround for the paragraph spacing bug and a pre-formatted attribution line:


{{quote|And bring us a lot of horilka, but not of that fancy kind with raisins, or with any other such things—bring us horilka of the purest kind, give us that demon drink that makes us merry, playful and wild!|[[Nikolai Gogol]]|''[[Taras Bulba]]''}}

Which results in:

And bring us a lot of horilka, but not of that fancy kind with raisins, or with any other such things—bring us horilka of the purest kind, give us that demon drink that makes us merry, playful and wild!
— Template:Comma separated entries

Punctuation

Template:Shortcut

Quotation marksSee also Quotations above.

The term quotation(s) in the material below also includes other uses of quotation marks such as those for titles of songs, chapters, and episodes; unattributable aphorisms; literal strings; "scare-quoted" passages and constructed examples.

Double or single
Quotations are enclosed within "double quotes".  Quotations within quotations are enclosed within 'single quotes'.
Inside or outside
Punctuation marks are placed inside the quotation marks only if the sense of the punctuation is part of the quotation (this system is referred to as logical quotation).



Correct:
Arthur said that the situation is "deplorable".



(When a sentence fragment is quoted, the period is outside.)


Correct:
Arthur said, "The situation is deplorable."



(The period is part of the quoted text.)


Correct:
Martha asked, "Are you coming?"



(When quoting a question, the question mark belongs inside because the quoted text itself was a question.)


Correct:
Did Martha say, "Come with me"?



(The very quote is being questioned, so here, the question mark is correctly outside; the period in the original quote is omitted.)

Note: This is not actually an American versus British English stylistic matter: at least one major British newspaper prefers typesetters' quotation (punctuation inside) and BBC News uses both styles; scientific and technical publications, even in the United States, almost universally use logical quotation (punctuation outside unless part of the source material), due to its precision; and much non-American English-language fiction uses the punctuation-inside method. Wikipedia uses logical quotation because, as an encyclopedia, it requires high standards of accuracy in the use of source material, and because logical quotation is far less prone to misquotation, ambiguity and the introduction of coding and other errors.

Article openings
When the title of an article appearing in the lead paragraph requires quotation marks (for example, the title of a song or poem), the quotation marks should not be in boldface, as they are not part of the title:



Correct:
"Jabberwocky" is a nonsense poem by Lewis Carroll.

Block quotes
As already noted above, we use quotation marks or block quotes (not both) to distinguish long quotations from other text. Multiparagraph quotations are always block-quoted.

Straight or curly?
There are two options when considering the look of the quotation marks (that is, the glyph):
Typewriter or straight style: "text", 'text', text's
Typographic or curly style: “text”, ‘text’, text’s
(Emphasis added to better distinguish between the glyphs.)
Grave and acute accents or backticks (`text´) are neither quotation marks nor apostrophes, and must not be used in their place.
Foreign characters that resemble apostrophes, such as Arabic ayin (ʿ) and alif (ʾ), are represented by their correct Unicode characters, despite possible display problems. If this is not feasible, use a straight apostrophe instead.
The exclusive use of straight quotes is recommended. The curly variants are harder to edit, since the characters are not on most keyboards. Mixed use interferes with searching (a search for Korsakoff's syndrome will fail to find Korsakoff’s syndrome and vice versa).
Whenever quotation marks or apostrophes appear in article titles, make a redirect from the same title but using the alternative glyphs.

Other matters

A quotation is not italicized simply because it is a quotation.
If an entire sentence is quoted in such a way that it becomes a grammatical part of the larger sentence, the first letter loses its capitalization ("It turned out to be true that 'a penny saved is a penny earned'.").
If a word or phrase appears in an article in single quotes, such as 'abcd', Wikipedia's search facility will find that word or phrase only if the search string is also within single quotes. This difficulty does not arise for double quotes, and this is one of the reasons the latter are recommended.

Brackets and parentheses

A bracketed phrase is enclosed by the punctuation of a sentence (as shown here). However, where one or more sentences are wholly inside brackets, their punctuation comes inside the brackets (see further details below). These rules apply to both round "( )" brackets, often called parentheses, and square "[ ]" brackets. There should not be a space next to a bracket on its inner side. An opening bracket should be preceded by a space, except in unusual cases; for example, when it is preceded by:

An opening quotation markHe rose to address the meeting: "(Ahem) ... Ladies and gentlemen, welcome!"Another opening bracketOnly the royal characters in the play ([Prince] Hamlet and his family) habitually speak in blank verse.A portion of a wordWe journeyed on the Inter[continental].

There should be a space after a closing bracket, except where another punctuation mark (other than an apostrophe or a hyphen) follows, and in unusual cases similar to those listed for opening brackets.
If sets of brackets must be nested, use the contrasting type (normally, square brackets appear within round brackets [like this]). Often, it is better to revise the sentence to reduce clutter, using commas, semicolons, colons or dashes instead.
Avoid adjacent sets of brackets—either put the parenthetic phrases in one set separated by commas, or rewrite the sentence. For example:




Incorrect:   
Nikifor Grigoriev (c. 1885–1919) (also known as Matviy Hryhoriyiv) was a Ukrainian insurgent leader.


Correct:
Nikifor Grigoriev (c. 1885–1919), also known as Matviy Hryhoriyiv, was a Ukrainian insurgent leader.


Correct:
Nikifor Grigoriev (c. 1885–1919) was a Ukrainian insurgent leader. He was also known as Matviy Hryhoriyiv.

Square brackets are used to indicate editorial replacements and insertions of text. They serve three main purposes:

To clarify. ("She attended [secondary] school"—where this was the intended meaning, but the type of school was unstated in the original sentence.)
To reduce the size of a quotation. If a source says "X contains Y, and under certain circumstances, X may contain Z as well", it is acceptable to reduce this to "X contains Y [and sometimes] Z",  without ellipsis. When an ellipsis (...; see below) is used to indicate material removed from a direct quotation, it should not normally be bracketed.
To make the grammar work: "She said that '[she] would not allow this' "—where her original statement was "I would not allow this." (Generally, though it is better to begin the quotation after the problematic word: "She said that she 'would not allow this.' ")

The use of square-bracketed wording should never alter the intended meaning of a quotation.

Sentences and brackets

If any sentence includes material that is enclosed in square or round brackets, it still must end—with a period, or a question or exclamation mark—after those brackets (a rule that applies in all English, whether British or U.S.). The preceding sentence is itself an example. This principle applies no matter what punctuation is used within the brackets.

Normally, if the words of a sentence begin within brackets, the sentence must also end within those brackets. There is an exception for matter that is added or modified editorially at the beginning of a sentence for clarity, usually in square brackets: " '[Principal Skinner] already told me that,' he objected."

A sentence that occurs within brackets in the course of another sentence does not have its first word capitalised just because it starts a sentence. The enclosed sentence may have a question mark or exclamation mark added, but not a period: "Alexander then conquered (who would have believed it?) most of the known world"; "Clare demanded that he drive (she knew he hated driving) to the supermarket." These constructions are usually best avoided, for readability.

Ellipses

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An ellipsis (plural ellipses) is a series of three dots. It marks the omission of material from quoted text.

Style
Ellipses have traditionally been implemented in three ways:
Three unspaced periods ( ... ). This is the easiest way, and gives a reliable appearance in HTML. Recommended.
Pre-composed ellipsis character ( … ; generated with the &hellip; character entity, or by insertion from the set below the edit window). This is harder to input and edit, and too small in some fonts. Not recommended.

Three spaced periods ( . . . ). This is an older style that is unnecessarily wide and requires non-breaking spaces to keep it from breaking at the end of a line. Strongly deprecated.

Function
Use an ellipsis if material is omitted in the course of a quotation, unless square brackets are used to gloss the quotation (see above, and the next point below). Put a space on each side of an ellipsis, except at the very start or end of a quotation. Sentence-final punctuation after an omission ellipsis is shown only if it is textually important (as is often the case with exclamation points and question marks, and rarely with periods); no space comes between the ellipsis and the terminal punctuation. Use non-breaking spaces (&nbsp;) only as needed to prevent improper line breaks, e.g.:
To keep a quotation mark from separating from the start of the quotation: "...&nbsp;we are still worried."
To keep the ellipsis from wrapping to the next line: "France, Germany,&nbsp;... and Belgium but not the USSR."

Pause or suspension of speech
Three periods are occasionally used to represent a pause in or suspense of speech, in which case the punctuation is retained in its original form (Virginia's startled reply was: "Could he...? No, I cannot believe it!"). This usage is avoided in other contexts in Wikipedia.

With square brackets
An ellipsis does not normally need square brackets around it, since its function is usually obvious—especially if the guidelines above are followed. But square brackets may optionally be used for precision, to make it clear that the ellipsis is not itself quoted; this is usually only necessary if the quoted passage also uses three period in it to indicate a pause or suspension. The ellipsis should follow exactly the principles given above, but with square brackets inserted immediately before and after it. (Her long rant continued: "How do I feel? How do you think I... look, this has gone far enough! [...] I want to go home!")

Serial commas

The serial comma (also known as the Oxford comma or Harvard comma) is a comma used immediately before a conjunction in a list of three or more items. The phrase ham, chips, and eggs is written with a serial comma, but ham, chips and eggs is not. Sometimes omitting the comma can lead to an ambiguous sentence, as in this example: The author would like to thank her parents, Sinéad O'Connor and President Bush.  Including the comma can also cause ambiguity, as in: The author would like to thank her mother, Sinéad O'Connor, and President Bush which may be a list of either two or three people. In such cases, there are three options for avoiding ambiguity:

A choice can be made whether to use or omit the comma after the penultimate item to avoid ambiguity.
The sentence can be recast to avoid listing the items in an ambiguous manner.
The items can be presented using a formatted list.

If the presence or absence of the final serial comma has no bearing on whether the sentence is ambiguous, there is no Wikipedia consensus on whether it should be used.

Colons

Colons (:) should not have spaces before them:




Correct:
He attempted it in two years: 1941 and 1943


Incorrect:   
He attempted it in two years : 1941 and 1943

Colons should have complete sentences before them:




Correct:
He attempted it in two years: 1941 and 1943


Incorrect:   
The years he attempted it included: 1941 and 1943

Hyphens

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Hyphens (-) indicate conjunction. There are three main uses.

To distinguish between homographs (re-dress = dress again, but redress = remedy or set right).
To link certain prefixes with their main word (non-linear, sub-section, super-achiever):
However, a clear tendency is emerging to join both elements in all varieties of English (subsection is now standard), particularly in North America (where nonlinear is also standard).
The hyphen is more likely to be used when the letters brought into contact are vowels, especially the same vowel (co-opt, pre-existing), or where a word is unusual or less expected in the context (co-proposed, re-target).
It is somewhat common not to hyphenate well-known and recognizable cases (coopt, preexisting, but not coowned, and probably not reanchor).
The hyphen is very often used to avoid doubling a or i: intra-atomic, juxta-articular, semi-intensive.
The hyphen is sometimes retained after sub- to avoid bringing two consonants into contact, and especially to avoid doubling b (subabdominal, but sub-basement). It is often retained for clarity when the main word begins with a vowel, or is short—especially when both of these apply (sub-era, not subera).
The hyphen is still often used after non-, and especially when n would be doubled (non-linear or nonlinear, as above; non-negotiable).
To link related terms in compound adjectives and adverbs:
Sometimes the hyphen helps with ease of reading (face-to-face discussion, hard-boiled egg); hyphens are particularly useful in long nominal groups where non-experts are part of the readership, such as in Wikipedia's scientific articles: gas-phase reaction dynamics.
Sometimes the hyphen helps with disambiguation (little-used car, not a reference to the size of a used car).
Many compound adjectives that are hyphenated when used attributively (before the noun they qualify—a light-blue handbag), are not hyphenated when used predicatively (after the noun—the handbag was light blue). Where there would be a loss of clarity, the hyphen may also be used in the predicative case (hand-fed turkeys, the turkeys were hand-fed).
Hyphens are often not used after -ly adverbs (wholly owned subsidiary), unless part of larger compounds (a slowly-but-surely strategy).
A hyphen is normally used when the adverb well precedes a participle used attributively (a well-meaning gesture; but normally a very well managed firm, since well itself is modified); and even predicatively, if well is necessary to, or alters, the sense of the adjective rather than simply intensifying it (the gesture was well-meaning, the child was well-behaved, but the floor was well polished).
A hanging hyphen is used when two compound adjectives are separated (two- and three-digit numbers, a ten-car or -truck convoy).
Values and units used as compound adjectives are hyphenated only where the unit is given as a whole word. Where hyphens are not used, values and units are always separated by a non-breaking space (&nbsp;).




Incorrect:
9-mm gap


Correct:
9 mm gap (rendered as 9&nbsp;mm gap)


Incorrect:   
9 millimetre gap


Correct:
9-millimetre gap


Correct:
12-hour shift


Correct:
12 h shift

Hyphens are never followed or preceded by a space, except when hanging or when used to display parts of words independently, such as the prefix sub- and the suffix -less.
Hyphens are used only to mark conjunctions; not to mark disjunction (for which en dashes are correct: see below).
Hyphenation involves many subtleties that cannot be covered here; but the rules and examples presented above illustrate the sorts of broad principles that inform current usage.

Dashes

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Several kinds of dash are used on Wikipedia.

En dashes

En dashes (–) have four distinct roles.

To indicate disjunction. In this role there are two main applications.
To convey the sense of to or through, particularly in ranges (pp. 211–19, 64–75%, the 1939–45 war, May–November) and where movement is involved (Dublin–Belfast route). Year and page ranges are often an issue on Wikipedia. The word to, rather than an en dash, is used when a number range involves a negative value or might be misconstrued as a subtraction (−3 to 1, not −3–1), or when the nearby wording demands it (he served from 1939 to 1941, not he served from 1939–1941).
As a substitute for some uses of and, to or versus for marking a relationship involving independent elements in certain compound expressions (Canada–US border, blood–brain barrier, time–altitude graph, 4–3 win in the opening game, male–female ratio, 3–2 majority verdict, Michelson–Morley experiment, diode–transistor logic; but a hyphen is used instead in Mon-Khmer languages which lacks a relationship, Sino-Japanese trade, in which Sino- lacks independence, and Indo-European linguistics which lacks both relationship and lexical independence).
Spacing: All disjunctive en dashes are unspaced, except when there is a space within either or both of the items (the New York – Sydney flight, the New Zealand – South Africa grand final, 3 July, 1888 – 18 August, 1940).
For negative signs and subtraction operators, as an alternative to the usually slightly shorter minus sign, − (input with &minus;). Negative signs (–8°C) are unspaced; subtraction signs (42 – 4 = 38) are spaced.  The en dash was the traditional typographic symbol for this operator, but now that unicode defines a character for this specific use, the minus is preferred.  In contexts such as code, where the text is intended to be copied and executed or evaluated, the ordinary hyphen works better and is preferred.
In lists, to separate distinct information within points—particularly track titles and durations, and musicians and their instruments, in articles on music albums. In this role, en dashes are always spaced.
As a stylistic alternative to em dashes (see below).

Hyphens have often been wrongly used in disjunctive expressions on Wikipedia; this is especially common in sports scores. When creating an article, a hyphen is now not used as a substitute for an en dash in the title.
The article on dashes includes input methods for typing dashes on several operating systems.

En dashes in page names

The en dash may be used in a page name, for example, Eye–hand span. Editors should provide a redirect page to such an article, using a hyphen in place of the en dash (e.g., Eye-hand span), to allow the name to be typed easily when searching Wikipedia. See also Wikipedia:Naming conventions (precision). Regardless of whether the page name includes a dash, the associated talk page name should match the page name exactly.

Em dashes

Em dashes (—) indicate interruption. They are used in the following two roles.

Parenthesis (Wikipedia—one of the most popular web sites—has the information you need). Here, a pair of em dashes is a more arresting way of nesting a phrase or clause than a pair of commas, and may be less intrusive than brackets. A pair of em dashes is particularly useful where there are already many commas; em dashes can make a sentence with more than one nesting easier to read, and sometimes they can remove ambiguity.
A sharp break in the flow of a sentence—sharper than is provided by a colon or a semicolon.

Em dashes are normally unspaced on Wikipedia.
Because em dashes are visually striking, Wikipedia takes care not to overuse them. A rule of thumb is to avoid more than two in a single paragraph, unless the paragraph is unusually long or the use of more than two em dashes would be logically cohesive. Only very rarely are there more than two em dashes in a single sentence.
The main article shows common input methods for em dashes on Macintosh and Windows.

Spaced en dashes as an alternative to em dashes

Spaced en dashes – such as here – can be used instead of em dashes in all of the ways discussed above. Spaced en dashes are used by several major publishers, to the complete exclusion of em dashes; style manuals more often prefer unspaced em dashes. One style should be used consistently in an article.

Other dashes

These are avoided on Wikipedia, notably the double-hyphen (--).

Spaces after the end of a sentence

There are no guidelines on whether to use one space after the end of a sentence, or two (French spacing), but the issue is not important, because the difference is only visible in the monospace edit boxes; it is ignored by browsers when displaying the article.

Slashes

Avoid joining two words by a slash (/, also known as a forward slash), as it suggests that the two are related, but does not specify how. It is often also unclear how the construct would be read aloud. Consider replacing a slash with an explanation, or adding one in a footnote.  Where possible, reword more fully to avoid uncertainties.
An example: The parent/instructor must be present at all times. Must both be present? (Then write the parent and the instructor.) Must at least one be present? (Then write the parent or the instructor.) Are they the same person? (Use a hyphen: the parent–instructor.) 
In circumstances involving a distinction or disjunction, the en dash is usually preferable to the slash, e.g., the novel–novella distinction.
An unspaced slash may be used:

To show pronunciations ("ribald is pronounced /ˈrıb·əld/")
To separate the numerator and denominator in a fraction (7/8 or Template:Frac)
To indicate regular defined yearly periods that do not coincide with calendar years (see Wikipedia:Manual of Style (dates and numbers)#Longer periods)
Where slashes are used in a phrase outside of Wikipedia, and using a different construction would be inaccurate, unfamiliar or ambiguous

A spaced slash may be used:

To separate run-in lines of poetry or song (To be or not to be: that is the question: / Whether 'tis nobler in the mind to suffer / The slings and arrows of outrageous fortune)
To separate any construction that can be separated with an unspaced slash when readability would be enhanced by doing so, most often when the items being separated are complex, such as involving a number of abbreviations, numbers; compare the NY 31 east / NY 370 exit with the NY 31 east/NY 370 exit.

Spaced slashes should be coded with a leading non-breaking space and a trailing normal space, e.g., x&nbsp;/ y (which renders as x / y), to prevent line breaks introducing readability problems.
The backslash character, \, is never used in place of a slash. 
It is preferred in general prose to use ÷ rather than / to represent mathematical division. (See Wikipedia:Manual of Style (dates and numbers)#Common mathematical symbols and Help:Displaying a formula for more information.)

And/or

The construct and/or is usually awkward. In general, where it is important to mark an inclusive or, use x or y, or both, rather than x and/or y. For an exclusive or, use either x or y, and optionally add but not both, if it is necessary to stress the exclusivity.  
Where more than two possibilities are presented, from which a combination is to be selected, it is even less desirable to use and/or. With two possibilities, at least the intention is clear; but with more than two it may not be. Instead of x, y, and/or z, use an appropriate alternative, such as one or more of x, y, and z; some or all of x, y, and z.

Question marks and exclamation marks

Question and exclamation marks are never preceded by a space in normal prose.
The exclamation mark is used with restraint: it is an expression of surprise or emotion that is generally unsuited to a scholarly or encyclopedic register.
Clusters of question marks, exclamation marks, or a combination of them (such as the interrobang) are highly informal and inappropriate in Wikipedia articles.
For the use of these marks in association with quotation marks, see #Quotations above.

Chronological items

See also: WP:MOSNUM#Dates of birth and death, WP:MOSNUM#Calendars, WP:MOSNUM#Time zones, and WP:MOSNUM#Autoformatting and linking

Precise language

Avoid statements that will date quickly, except on pages that are regularly refactored, such as those that cover current events. Avoid such items as recently and soon (unless their meaning is clear in a storyline), currently (except on rare occasions when it is not redundant), in modern times, is now considered and is soon to be superseded. Instead, use either:

more precise items (since the start of 2005; during the 1990s; is expected to be superseded by 2008); or
an as of phrase (as of August 2007), which is a signal to readers of the time-dependence of the statement, and to later editors of the need to update the statement (see As of).

Times

Context determines whether the 12- or 24-hour clock is used; in both, colons separate hours, minutes and seconds (1:38:09 pm and 13:38:09).

12-hour clock times end with dotted or undotted lower-case a.m. or p.m., or am or pm, which are spaced (2:30 p.m. or 2:30 pm, not 2:30p.m. or 2:30pm). Noon and midnight are used rather than 12 pm and 12 am; whether midnight refers to the start or the end of a date will need to be specified unless this is clear from the context.
24-hour clock times have no a.m., p.m., noon or midnight suffix. Discretion may be used as to whether the hour has a leading zero (08:15 or 8:15). 00:00 refers to midnight at the start of a date, 12:00 to noon, and 24:00 to midnight at the end of a date.

DatesWikipedia does not use ordinal suffixes or articles, or put a comma between month and year.




Incorrect:   
June 25th, 25th June, the 25th of June


Correct:
14 February, February 14


Incorrect:
October, 1976


Correct:
October 1976

Date ranges are preferably given with minimal repetition (5–7 January 1979; September 21–29, 2002), using an unspaced en dash. If the autoformatting function is used, the opening and closing dates of the range must be given in full (see Autoformatting and linking) and be separated by a spaced en dash.
Rarely, a night may be expressed in terms of the two contiguous dates using a slash (the bombing raids of the night of 30/31 May 1942); this cannot be done using the autoformatting function.
Yearless dates (5 March, March 5) are inappropriate unless the year is obvious from the context. There is no such ambiguity with recurring events, such as "January 1 is New Year's Day".
ISO 8601 dates (1976-05-13) are uncommon in English prose and are generally not used in Wikipedia. However, they may be useful in long lists and tables for conciseness and ease of comparison.

Longer periods

Months are expressed as whole words (February, not 2), except in the ISO 8601 format. Abbreviations such as Feb are used only where space is extremely limited, such as in tables and infoboxes. Do not insert of between a month and a year (April 2000, not April of 2000).

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Seasons. Because the seasons are reversed in each hemisphere (and areas near the equator tend to have just wet and dry seasons), neutral wording may be preferable (in early 1990, in the second quarter of 2003, around September). Consider using a date or month rather than a season name, unless there is a logical connection (the autumn harvest). In any case, avoid frank ambiguities like  "Apollo 11 landed on the Moon in the summer of 1969". Seasons are normally spelled with a lower-case initial.
Years
Years are normally expressed in digits; a comma is not used in four-digit years (1988, not 1,988).
Avoid inserting the words the year before the digits (1995, not the year 1995), unless the meaning would otherwise be unclear.
Either CE and BCE or AD and BC can be used—spaced, undotted (without periods) and upper-case. Choose either the BC-AD or the BCE-CE system, but not both in the same article. AD appears before or after a year (AD 1066, 1066 AD); the other abbreviations appear after (1066 CE, 3700 BCE, 3700 BC). The absence of such an abbreviation indicates the default, CE-AD. It is inappropriate for a Wikipedia editor to change from one style to another unless there is some substantial reason for the change; the Manual of Style favors neither system over the other.
Uncalibrated (bce) radiocarbon dates: Do not give uncalibrated radiocarbon dates (represented by the lower-case bce unit, occasionally bc or b.c. in some sources), except in directly quoted material, and even then include a footnote, a [square-bracketed editor's note], or other indication to the reader what the calibrated date is, or at least that the date is uncalibrated. Calibrated and uncalibrated dates can diverge surprisingly widely, and the average reader does not recognize the distinction between bce and BCE-BC.
Year ranges, like all ranges, are separated by an en dash (do not use a hyphen or slash (2005–08, not 2005-08 or 2005/08). A closing CE-AD year is normally written with two digits (1881–86) unless it is in a different century from that of the opening year (1881–1986). The full closing year is acceptable, but abbreviating it to a single digit (1881–6) or three digits (1881–886) is not. A closing BCE-BC year is given in full (2590–2550 BCE). While one era signifier at the end of a date range still requires an unspaced en dash (12–5 BC), a spaced en dash is required when a signifier is used after the opening and closing years (5 BC – 29 AD).
A slash may be used to indicate regular defined yearly periods that do not coincide with calendar years (the financial year 1993/4).
Abbreviations indicating long periods of time ago—such as BP (before present), as well as various annum-based units such as Ka (kiloannum) and kya (thousand years ago), Ma (megaannum) and mya (million years ago), and Ga (gigaannum or billion years ago)—are given as full words and wikilinked on first occurrence.
To indicate around, approximately, or about, the abbreviations c. and ca. are preferred over circa, approximately or approx., and are spaced (c. 1291).  Use a question mark instead (1291?) only if the date is in fact questioned rather than approximate. (The question mark may mistakenly be understood as a sign that editors have simply not checked the date.)
Decades contain no apostrophe (the 1980s, not the 1980's); the two-digit form is used only where the century is clear (the '80s or the 80s).
Centuries and millennia
There was no year 0. So for dates AD (or CE) the 1st century was 1–100, the 17th century was 1601–1700, and the second millennium was 1001–2000; for dates BC (or BCE) the 1st century was 100–1; the 17th century was 1700–1601, and the second millennium was 2000–1001.
Use numerals for centuries (the 17th century), except at the start of a sentence; do not capitalize century.
Because expressions like the 1700s are ambiguous (referring to a century or a decade), they are best avoided.

NumbersSee also: WP:MOSNUM#Non-base-ten notations and WP:MOSNUM#Natural numbers

Numbers as figures or wordsGeneral rule

In the body of an article, single-digit whole numbers (from zero to nine) are given as words; numbers of more than one digit are generally rendered as figures, or as words if they are expressed in one or two words (sixteen, eighty-four, two hundred, but 3.75, 544, 21 million).

Exceptions

The numerical elements of dates and times are never given as words (that is, never the seventh of January or twelve forty-five p.m.; but specific references such as Daniel Webster's Seventh of March speech, should follow standard usage for the topic).
Numbers that open a sentence are given as words; alternatively, the sentence can be recast so that the number is not in first position.
In tables and infoboxes, all numbers are expressed as numerals.
Within a context or a list, style should be consistent (either There were 5 cats and 32 dogs or There were five cats and thirty-two dogs, not There were five cats and 32 dogs).
On rare occasions when figures may cause confusion, use words instead (thirty-six 6.4-inch rifled guns, not 36 6.4-inch rifled guns).
Fractions are given as words unless they occur in a percentage or with an abbreviated unit (⅛ mm, but never an eighth of a mm), or are mixed with whole numerals.
Ordinal numbers are given as words using the same rules as for cardinal numbers. The exception is ordinals for centuries, which are always expressed in figures (the 5th century CE; 19th-century painting). The ordinal suffix (e.g., th) is not superscripted (23rd and 496th, not 23^rd and 496^th).
Proper names and formal numerical designations comply with common usage (Chanel No. 5, 4 Main Street, 1-Naphthylamine, Channel 6). This is the case even where it causes a numeral to open a sentence, although this is usually avoided by rewording.

Hyphenation

Two-word numbers from 21 to 99 are hyphenated when presented as words (fifty-six), as are fractions (seven-eighths). Do not hyphenate other multi-word numbers (five hundred, not five-hundred).

Large numbers

See also: Wikipedia:Manual of Style (dates and numbers)#Magnitude prefixes, Order of magnitude, and Long and short scales

Commas are used to break the sequence every three places (2,900,000).
Large rounded numbers are generally assumed to be approximations; only where the approximation could be misleading is it necessary to qualify with about or a similar term.
Avoid over-precise values where they are unlikely to be stable or accurate, or where the precision is unnecessary in the context. (The speed of light in a vacuum is 299,792,458 metres per second is probably appropriate, but The distance from the Earth to the Sun is 149,014,769 kilometres and The population of Cape Town is 2,968,790 would usually not be, because both values are unstable at that level of precision, and readers are unlikely to care in the context.)
Scientific notation (5.8 × 10⁷) is preferred in scientific contexts.
Where values in the millions occur a number of times through an article, upper-case M may be used for million, unspaced, after using the full word at the first occurrence. (She bequeathed her fortune of £100 million unequally: her eldest daughter received £70M, her husband £18M, and her three sons each just £4M each.)
Billion is understood as 10⁹. After the first occurrence in an article, billion may be abbreviated to unspaced bn ($35bn).

Decimal points

A decimal point is used between the integral and the fractional parts of a decimal; a comma is never used in this role (6.57, not 6,57).
The number of decimal places should be consistent within a list or context (The response rates were 41.0 and 47.4 percent, respectively, not The response rates were 41 and 47.4 percent, respectively), except in the unusual instances where the items were measured with unequal precision.
Numbers between minus one and plus one require a leading zero (0.02, not .02); exceptions are performance averages in sports where a leading zero is not commonly used, and commonly used terms such as .22 caliber.

Percentages

Percent or per cent are commonly used to indicate percentages in the body of an article. The symbol % may be more common in scientific or technical articles, or in complex listings.
The symbol is unspaced (71%, not 71 %).
In tables and infoboxes, the symbol is used, not the words percent or per cent.
Ranges are preferably formatted with one rather than two percentage signifiers (22–28%, not 22%–28%).

Units of measurement

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Which system to use

For US-related articles, the main units are US units; for example, 10 miles (16 km).
For UK-related, the main units are either metric or imperial (consistently within an article).
For other country-related articles, the main units are metric; for example, 16 kilometres (10 mi).
American English spells metric units with final -er (kilometer); in all other varieties of English, including Canadian, -re is used (kilometre).
In scientific articles, use the units employed in the current scientific literature on that topic. This will usually be SI, but not always. For example, natural units are often used: ångströms (or angstroms) are widely used in such fields as x-ray crystallography and structural chemistry, and Hubble's constant should be quoted in its most common unit of (km/s)/Mpc rather than its SI unit of s⁻¹.
If editors cannot agree on the sequence of units, put the source value first and the converted value second. If the choice of units is arbitrary, use SI units as the main unit, with converted units in parentheses.

Conversions

Conversions to and from metric and US units should generally be provided. There are two exceptions:
scientific articles where there is consensus among the contributors not to convert the metric units, in which case the first occurrence of each unit should be linked;
where inserting a conversion would make a common expression awkward (The four-minute mile).
In the main text, give the main units as words and use unit symbols or abbreviations for conversions in parentheses; for example, a pipe 100 millimetres (4 in) in diameter and 16 kilometres (10 mi) long or a pipe 4 inches (100 mm) in diameter and 10 miles (16 km) long. The exception is that where there is consensus to do so, the main units may also be abbreviated in the main text after the first occurrence.
Converted values should use a level of precision similar to that of the source value; for example, the Moon is 380,000 kilometres (240,000 mi) from Earth, not (236,121 mi). The exception is small numbers, which may need to be converted to a greater level of precision where rounding would be a significant distortion; for example, one mile (1.6 km), not one mile (2 km).
Category:Conversion templates can be used to convert and format many common units, including Template:T1, which includes non-breaking spaces.
In a direct quotation:
conversions required for units cited within direct quotations should appear within square brackets in the quote;
if the text contains an obscure use of units (e.g., five million board feet of lumber), annotate it with a footnote that provides standard modern units, rather than changing the text of the quotation.
Where footnoting or citing sources for values and units, identify both the source and the original units.

Unit symbols and abbreviations

Standard abbreviations and symbols for units are undotted (do not carry periods). For example, m for meter and kg for kilogram (not m. or kg.), in for inch (not in.,  or ″), ft for foot (not ft., or ′) and lb for pound (not lb. or #).
The degree symbol is °. Using any other symbol (e.g., masculine ordinal º or "ring above" ˚) for this purpose is incorrect.
Do not append an s for the plurals of unit symbols (kg, km, in, lb, not kgs, kms, ins, lbs).
Temperatures are always accompanied by °C for Celsius, °F for Fahrenheit, or K for kelvin (35 °C, 62 °F, and 5,000 K, not 5,000 °K); the words for these three terms always have an upper-case initial.
Values and unit symbols are spaced (25 kg, not 25kg). The exceptions are degrees, minutes and seconds for angles and coordinates (the coordinate is 5° 24′ 21.12″ N, the pathways are at a 180° angle, but the average temperature is 18 °C).
Squared and cubic metric-symbols are always expressed with a superscript exponent (5 km², 2 cm³); squared imperial-unit abbreviations are rendered with sq, and cubic with cu (15 sq mi, 3 cu ft). A superscript exponent indicates that the unit is squared, not the unit and the quantity (3 meters squared is 9 square meters, or 9 m²; 8 miles squared is 64 square miles).
In tables and infoboxes, use symbols and abbreviations for units, not words.
Some different units share the same name. These examples show the need to be specific.
Use US or imperial gallon rather than just gallon.
Use nautical or statute mile rather than mile in nautical and aeronautical contexts.
Use long ton or short ton rather than just ton (the metric unit—the tonne—is also known as the metric ton).
Ranges are preferably formatted with one rather than two unit signifiers (5.9–6.3 kg, not 5.9 kg – 6.3 kg).

Unnecessary vagueness

Use accurate measurements whenever possible.




Vague:
The wallaby is small.


Precise:   
The typical male wallaby is 1.6 metres (63 in) from head to tail.


Vague:
Prochlorococcus marinus is a tiny cyanobacterium.


Precise:
The cyanobacterium Prochlorococcus marinus is 0.5 to 0.8 micrometres across.


Vague:
The large herd of dugong stretched a long way down the coast.


Precise:
The dugong swam down the coast in a herd five kilometres (3 mi) long and 300 metres (1000 ft) wide.

Currencies

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See also: Wikipedia:WikiProject Numismatics/Style#Article titlesWhich one to use

In country-specific articles, such as Economy of Australia, use the currency of the country.
In non-country-specific articles such as Wealth, use US dollars  (US$123).

Formatting

Fully identify a currency on its first appearance (AU$52); subsequent occurrences are normally given without the country identification (just $88), unless this would be unclear. The exception to this is in articles related to the US and the UK, in which the first occurrence may also be shortened ($34 and £22, respectively), unless this would be unclear.
Do not place a currency symbol after the value (123$, 123£), unless the symbol is normally written thus. Do not write $US123 or $123 (US).
Currency abbreviations that come before the number are unspaced if they end in a symbol (£123, €123), and spaced if they end in an alphabetical character (R 75). Do not place EU or a similar prefix before the € sign.
If there is no common English abbreviation or symbol, use the ISO 4217 standard.
Ranges are preferably formatted with one rather than two currency signifiers ($250–300, not $250–$300).
Conversions of less familiar currencies may be provided in terms of more familiar currencies, such as the euro or the US dollar. Conversions should be in parentheses after the original currency, with the year given as a rough point of reference; for example, 1,000 Swiss francs (US$763 in 2005), rounding to the nearest whole unit.
Consider linking the first occurrence of a symbol for less well-known currencies (₮146); it is generally unnecessary to link the symbols of well-known currencies.

Common mathematical symbolsSee also: Wikipedia:Manual of Style (mathematics)

For a negative sign or subtraction operator, use a minus sign (−), input by clicking on it in the insert box beneath the edit window or by keying in &minus;), or an en dash (see En dashes); do not use a hyphen, unless writing code.
For a multiplication sign, use ×, which is input by clicking on it in the edit toolbox under the edit window or by keying in &times; (however, the unspaced letter x is accepted as a substitute for by in such terms as "4x4").
The following signs are spaced on both sides:
plus, minus, plus or minus (as operators): +  −  ±
multiplication and division: ×  ÷
equals, does not equal, equals approximately: =  ≠  ≈
is less than, is less than or equal to, is greater than, is greater than or equal to: <  ≤  >  ≥

Simple tabulation

Lines that start with blank spaces in the editing window are displayed boxed and in a fixed-width font, for simple tabulation. Lines that contain only a blank space insert a blank line into the table. For a complete guide to constructing tables, see Meta:Help:Table.

UsagePossessivesFor thorough treatment of the English possessive see Apostrophe.

It's is the short form of it is or it has; counterintuitively, the possessive its has no apostrophe.
Usage varies for the possessive of singular nouns ending in s. Maintain consistency (James' house or James's house, but not both in the same article). Some forms almost always take an extra s (Ross's father); some usually do not (Socrates' wife; Moses' ascent of Sinai; Jesus' last words).

Latin abbreviations

Abbreviations of Latin terms such as i.e. and e.g., or the use of the Latin terms in full, such as nota bene, or vide infra, should be left as the original author wrote them. When used in the main text, the abbreviations should normally be in roman rather than italic face. However, articles intended for a general audience will be more widely understood if English terms such as that is and for example are used instead.

Avoid first-person pronouns

Wikipedia articles must not be based on one person's opinions or experiences; thus, I is never used, except when it appears in a quotation. For similar reasons, avoid we; a sentence such as We should note that some critics have argued in favor of the proposal sounds more personal than encyclopedic.
Nevertheless, it is sometimes appropriate to use we when referring to an experience that any reader would be expected to have, such as general perceptual experiences. For example, although it might be best to write When most people open their eyes, they see something, it is still legitimate to write When we open our eyes, we see something.
It is also acceptable to use we in mathematical derivations (To normalize the wavefunction, we need to find the value of the arbitrary constant A). In historical fields, we can mean the modern world as a whole (The text of De re publica has come down to us with substantial sections missing).

Avoid second-person pronouns

Use of the second person (you), which is often ambiguous and contrary to the tone of an encyclopedia, is discouraged.  
Instead, refer to the subject of the sentence or use the passive voice, for example:




Use:
When a player moves past "Go", that player collects $200.


Use:
Players passing "Go" collect $200.


Use:
$200 is collected when passing "Go".


Do not use:   
When you move past "Go", you collect $200.

This guideline does not apply to quoted text, which should be quoted exactly, nor to the Wikipedia namespace, where you refers to the writers to whom articles in the namespace are addressed.

Avoid contested vocabulary

Words and phrases like thusly, overly, whilst, as per, refute in the sense of dispute, along with several others, should be avoided because they not widely accepted—at least in some of their applications. Some are regional, so unsuitable in an international encyclopedia (see National varieties of English, below). Some give an impression of "straining for formality", and therefore of an insecure grasp of English. For a collection of contested words see List of English words with disputed usage; for a larger collection of words that are often misused or confused see List of frequently misused English words. See also Identity and Gender-neutral language, below.

Avoid contractions

In general, the use of contractions—such as don't, can't, won't, they'd, should've, it's—is informal and should be avoided. Contractions should be left unchanged, however, when they occur in a quotation.

Avoid instructional and presumptuous language

It is usually preferable to avoid such phrases as remember that and note that, which address readers directly in an unencyclopedic tone. Similarly, phrases such as of course, naturally, and obviously make presumptions about readers' knowledge, and call into question the reason for including the related information in the first place.

National varieties of English

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See also: Wikipedia:Manual of Style (spelling)



The English Wikipedia has no general preference for a major national variety of the language. No variety is more correct than the others. Users are asked to take into account that the differences between the varieties are superficial. Cultural clashes over spelling and grammar are avoided by using four simple guidelines.  The accepted style of punctuation is covered in the punctuation section.

Consistency within articles

Each article should consistently use the same conventions of spelling and grammar. For example, center and centre are not to be used in the same article. The exceptions are:

quotations (the original variety is retained);
titles (the original spelling is used, for example United States Department of Defense and Australian Defence Force); and
explicit comparisons of varieties of English.

Strong national ties to a topic

An article on a topic that has strong ties to a particular English-speaking nation uses the appropriate variety of English for that nation. For example:

American Civil War—(American English)
Tolkien's The Lord of the Rings—(British English)
Australian Defence Force—(Australian English)
European Union institutions—(British English)
Vancouver—(Canadian English)

Retaining the existing variety

If an article has evolved using predominantly one variety, the whole article should conform to that variety, unless there are reasons for changing it on the basis of strong national ties to the topic. In the early stages of writing an article, the variety chosen by the first major contributor to the article should be used, unless there is reason to change it on the basis of strong national ties to the topic. Where an article that is not a stub shows no signs of which variety it is written in, the first person to make an edit that disambiguates the variety is equivalent to the first major contributor.

Opportunities for commonality

Wikipedia tries to find words that are common to all varieties of English.

In choosing words or expressions, especially for article titles, there may be value in making choices that avoid varying spellings, where possible. In extreme cases of conflicting names, a common substitute (such as fixed-wing aircraft) is favored over national varieties (fixed-wing aeroplanes [British English], and fixed-wing airplanes [American English]).
If a variable spelling appears in an article name, redirect pages are made to accommodate the other variants, as with Artefact and Artifact, so that they can always be found in searches and linked to from either spelling.
Sensitivity to terms that may be used differently between different varieties of English allows for wider readability; this may include glossing terms and providing alternative terms where confusion may arise. Insisting on a single term or a single usage as the only correct option does not serve well the purposes of an international encyclopedia.
Use an unambiguous word or phrase in preference to one that is ambiguous because of national differences. For example, use alternative route (or even other route) rather than alternate route, since alternate means only "alternating" to a British English speaker.

Articles such as English plural and American and British English differences provide information on the differences between the major varieties of the language.

Foreign terms

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Foreign words are used sparingly.

No common usage in English
Wikipedia prefers italics for phrases in other languages and for isolated foreign words that do not yet have common usage in English. However, in an article on a subject for which there is no English-language term, the foreign term does not require italicization.
Common usage in English
Loanwords and -phrases that have common usage in English—praetor, Gestapo, samurai, esprit de corps—do not require italicization. A rule of thumb is: do not italicize words that appear in an English language dictionary.
Spelling and transliteration
For terms in common usage, use anglicized spellings; native spellings are an optional alternative if they use the Latin alphabet. Diacritics are optional, except where they are required for disambiguation (résumé). Where native spellings in non-Latin scripts (such as Greek and Cyrillic) are given, they appear in parentheses (except where the sense requires otherwise), and are not italicized, even where this is technically feasible. The choice between anglicized and native spellings should follow English usage (e.g., Besançon, Edvard Beneš and Göttingen, but Nuremburg,  role, and Florence). Article titles follow our naming conventions.

Identity

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Use terminology that subjects use for themselves (self-identification) whenever this is possible. Use terms that a person uses for himself or herself, or terms that a group most commonly uses for itself.
A transgender, transsexual or genderqueer person's latest preference of name and pronoun should be adopted when referring to any phase of that person's life, unless this usage is overridden by that person's own expressed preference as to how this should be managed. Nevertheless, write to avoid confusing or seemingly logically impossible text that could result from pronoun usage (e.g., she fathered her first child).
Use specific terminology. For example, often it is more appropriate for people from Ethiopia (a country in Africa) to be described as Ethiopian, not carelessly (with the risk of stereotyping) as African.
To counter an interpretation that is inappropriately essentialist, terms used to describe people should qualify other nouns (black people, not blacks; gay people, not gays). Some groups, however, prefer the direct noun (many Jews, for example, prefer to use that noun rather than Jewish people).
The term Arab (never to be confused with Muslim or Islamic) refers to people and things of ethnic Arab origin. The term Arabic refers to the Arabic language or writing system, and related concepts (Not all Arab people write or converse in Arabic.)
As always in a direct quotation, use the original text, even if the quoted text is judged unsatisfactory by the preceding guidelines.

Gender-neutral language

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Please consider using gender-neutral language where this can be achieved in tidy wording and without loss of precision. This recommendation does not apply to direct quotations, the titles of works (The Ascent of Man), or where all referents are of one gender, such as in an all-female school (if any student broke that rule, she was severely punished).

Images

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The following general guidelines should be followed in the absence of a compelling reason to do otherwise.

Start an article with a right-aligned image.
Multiple images in the same article can be staggered right-and-left (Example: Timpani).
Avoid sandwiching text between two images facing each other.
Generally, right-alignment is preferred to left- or center-alignment. (Example: Race (classification of human beings)).
Exception: Portraits with the head looking to the reader's right should be left-aligned (looking into the text of the article) when this does not interfere with navigation or other elements. In such cases, it may be appropriate to move the Table of Contents to the right by using {{TOCright}}.  Since faces are not perfectly symmetrical, it is generally inadvisable to use photo editing software to reverse a right-facing portrait image; however, some editors employ this controversial technique when it does not alter obvious non-symmetrical features (such as Mikhail Gorbachev's birthmark) or make text in the image unreadable.
If there are too many images in a given article, consider using a gallery.
Do not place left-aligned images directly below second-level (===) headings, as this disconnects the heading from the text it precedes. For example, do not use:

=== Section 1b ===
[[Image:Image relating to section 1b.jpg|frame|left|]]
First paragraph of section 1b.

Instead, either right-align the image, remove it, or move it to another relevant location.

Use {{Commons}} to link to more images on Commons, wherever possible.
Use captions to explain the relevance of the image to the article (see #Captions).
Specifying the size of a thumbnail image is not recommended: without specifying a size, the width will be what readers have specified in their user preferences, with a default of 180px (which applies for most readers), and a maximum of 300px. However, the image subject or image properties may call for a specific image width to enhance the readability or layout of an article. Cases where a specific image width is appropriate include:
images with extreme aspect ratios
detailed maps, diagrams or charts
images in which a small region is relevant, but cropping to that region would reduce the coherence of the image
a lead image that captures the essence of the article (recommended not to be smaller than 300px, as this will make the image smaller for users who have set 300px in their user preferences).

Some users need to configure their systems to display large text; forced large thumbnails can leave little width for text, making reading difficult.

The current image markup for landscape-format and square images is:

[[Image:picture.jpg|thumb|right|Insert caption here]]

and for portrait-format images:

[[Image:picture.jpg|thumb|upright|right|Insert caption here]]

This will result in default image width of 180px and 140px respectively, which may vary proportionately by user preferences. Image rendering in this markup does not depend on image height.

CaptionsMain article: Wikipedia:Captions

Usage

Photographs and other graphics always have captions, unless they are "self-captioning" (such as in reproductions of album or book covers) or when they are unambiguous depictions of the subject of the article. For example, in a biography article, a caption is not mandatory for a portrait of the subject pictured alone, but might contain the name of the subject and additional information relevant to the image.

Formatting

Captions always start with a capital letter.
Most captions are not complete sentences, but extended phrases, which should not finish with a period.
Complete sentences in captions always end in a period.
Captions should not be italicized, except for words that would otherwise be italicized.
Captions should be succinct; more information on the file can be included in the image or media description page, or in the main text.

Bulleted and numbered listsSee also: Help:List and Wikipedia:List guideline

Do not use lists if a passage reads easily using plain paragraphs.
Use numbers rather than bullets only if:
there is a need to refer to the elements by number;
the sequence of the items is critical; or
the numbering has value of its own, for example in a track listing.
All elements in a list should use the same grammatical form and should be consistently either complete sentences or sentence fragments.
When the elements are complete sentences, they are formatted using sentence case and a final period.
When the elements are sentence fragments, they are typically introduced by a lead fragment ending with a colon, are formatted using consistently either sentence or lower case, and finish with a final semicolon or no punctuation, except that the last element typically finishes with a final period.

LinksWikilinksMain article: Wikipedia:Manual of Style (links)

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Make links only where they are relevant to the context. It is not useful and can be very distracting to mark all possible words as hyperlinks. Links should add to the user's experience; they should not detract from it by making the article harder to read. A high density of links can draw attention away from the high-value links that you would like your readers to follow up. Redundant links clutter the page and make future maintenance harder. A link is the equivalent of a footnote in a print medium. Imagine if every second word in an encyclopedia article were followed by "(see: ...)". Hence, links should not be so numerous as to make the article harder to read. 
Check links: After linking, ensure that the destination is the intended one; many dictionary words lead to disambiguation pages and not to complete articles on a concept. An anchor into a targeted page—the label after a pound/hash sign (#) in a URL—will get readers to the relevant area within that page.
Initial capitalization: Wikipedia's MediaWiki software does not require that wikilinks begin with an upper-case character. Only capitalize the first letter where this is naturally called for, or when specifically referring to the linked article by its name:

Snakes are often venomous, but lizards only rarely (see Poison).

Piped links: The use of piped links can be avoided in many cases when adding a grammatical suffix to a wikilink that is not part of an article title, by placing the suffix outside the brackets. The suffix will still appear as part of the link, but will not be included in the link's target. For example, the markup [[transformer]]s appears in the article text as transformers, but links to the article Transformer.

External linksMain article: Wikipedia:External links

Articles can include an external links section at the end to list links to websites outside of Wikipedia for purposes of providing further information as opposed to citing sources.  The standard format is a primary heading named == External links == followed by a bulleted list of links. External links should identify the link and briefly summarize the website's contents and why the website is relevant to the article. For example:

*[http://history.nih.gov/exhibits/history/index.html History of NIH]

*[http://www.nih.gov/ National Institutes of Health homepage]

When wikified, the link will appear as:

History of NIH
National Institutes of Health homepage

Refrain from using too many links in articles: a sea of speckled blue often looks messy.

MiscellaneousKeep markup simple

Use the simplest markup to display information in a useful and comprehensible way. Markup may appear differently in different browsers. Use HTML and CSS markup sparingly and only with good reason. Minimizing markup in entries allows easier editing.
In particular, do not use the CSS float or line-height properties because they break rendering on some browsers when large fonts are used.

Formatting issues

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Formatting issues such as font size, blank space and color are issues for the Wikipedia site-wide style sheet and should not be dealt with in articles except in special cases. If you absolutely must specify a font size, use a relative size, that is, font-size: 80%; not an absolute size, for example, font-size: 8pt. It is also almost never a good idea to use other style changes, such as font family or color.
Typically, the usage of custom font styles will

reduce consistency—the text will no longer look uniform with typical text;
reduce usability—it will likely be impossible for people with custom stylesheets (for accessibility reasons, for example) to override it, and it might clash with a different skin as well as bother people with color blindness; and
increase arguments—there is the possibility of other Wikipedians disagreeing with choice of font style and starting a debate about it for aesthetic purposes.

For such reasons, it is typically not good practice to apply inline CSS for font attributes in articles.

Color codingMain article: Wikipedia:Accessibility

Using color alone to convey information (color coding) should not be done.  This is not accessible to people with color blindness (especially monochromacy), on black-and-white printouts, on older computer displays with fewer colors, on monochrome displays (PDAs, cell phones), and so on.
If it is necessary to use colors, try to choose colors that are unambiguous (such as orange and violet) when viewed by a person with red-green color blindness (the most common type). In general, this means that shades of red and green should not both be used as color codes in the same image. Viewing the page with Vischeck can help with deciding if the colors should be altered.  
It is certainly desirable to use color as an aid for those who can see it, but the information should still be accessible without it.

Invisible comments

Editors use invisible comments to communicate with each other in the body of the text of an article. These comments are visible only in the wiki source (i.e., the edit box), not when normally reading the page.
Invisible comments are useful for flagging an issue or leaving instructions concerning a specific part of the text, where this is more convenient than raising the matter on the talk page.
To leave an invisible comment, enclose the text which you intend to be read only by editors within <!-- and -->.
For example:

(Inline:) ... dysoproxil fumerates.<!--Check my insertion of "s" --> These compounds have major uses in ...

(Immediately after a section title:) <!--Do not change this section title: there are links to it.-->

(At the top of the wiki source:) <!--This article is written in AmEng.-->

Invisible comments should be used judiciously, since they can clutter the wiki source for other editors and often will need to be removed by another editor when addressed. Check that your invisible comment does not change the formatting on the normal page, such as introducing unwanted white space.

Vague:	The wallaby is small.
Precise:	The typical male wallaby is 1.6 metres (63 in) from head to tail.
Vague:	Prochlorococcus marinus is a tiny cyanobacterium.
Precise:	The cyanobacterium Prochlorococcus marinus is 0.5 to 0.8 micrometres across.
Vague:	The large herd of dugong stretched a long way down the coast.
Precise:	The dugong swam down the coast in a herd five kilometres (3 mi) long and 300 metres (1000 ft) wide.