This guideline covers the use of abbreviations—including acronyms and initialisms, contractions, and other shortenings—in the English Wikipedia.

Maintaining a consistent abbreviation style allows Wikipedia to be read, written, edited, and navigated more easily by readers and editors. The style should always be consistent within a page. If a guideline conflicts with the correct usage of a proper name, ignore it. Abbreviations in quotations from written sources should always be written exactly as in the source, unless it is a Wikipedia-made translation.

Always consider whether it is better to write a word or phrase out in full, thus avoiding potential confusion for those not familiar with its abbreviation. Remember that Wikipedia does not have the same space constraints as paper.

Avoid making up new abbreviations, especially acronyms. For example, "International Feline Federation" is good as a translation of Fédération Internationale Féline, but neither the anglicisation nor the reduction IFF is used by the organisation; use the original name and its official abbreviation, FIFe.

If it is necessary to abbreviate in small spaces (infoboxes, navboxes and tables), use widely recognised abbreviations. As an example, for New Zealand gross national product, use NZ and GNP, with a link if the term has not already been written out: NZ GNP; do not use the made-up initialism NZGNP).

Modern style is to use a full point (period) after a shortening (see § Shortenings for exceptions) but no full points within an acronym or initialism. In the unusual case of an acronym containing full points between letters, it should also have a full point after the final letter. If an abbreviation ending in a full point ends a sentence, do not use an extra full point (e.g. They lived near Courtyard Sq., not They lived near Courtyard Sq..).

Contractions that contain an apostrophe (don't, shouldn't, she'd) never take a period, except at the end of a sentence. They are also not used in encyclopedia content except in quotations or titles of works, as noted below. Contractions that do not contain an apostrophe almost always take a period in North American English, but not in British English when the contraction ends with the same letter as the full term: Doctor can be abbreviated Dr. in American and Canadian English, but is Dr in British English. If the dot-less usage could be confusing in the context, use the point. Exceptions are symbols of units of measurement, which never use periods (see WP:Manual of Style/Dates and numbers).

Do not apply initial capitals or other forms of emphasis to common-noun phrases just because capitals are used when abbreviating them:

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

Similarly, when showing the source of an acronym, initialism, or syllabic abbreviation, emphasizing the letters in the expansion that make up the acronym is unnecessary and potentially distracting:

• Incorrect: FOREX (FOReign EXchange)
• Incorrect: FOREX (foreign exchange)
• Incorrect: FOREX (foreign exchange)
• Correct: FOREX (foreign exchange)

Acronyms are abbreviations formed, usually, from the initial letters of words in a phrase.

An initialism is an abbreviation formed from some or all of the initial letters of words in a phrase. An acronym is sometimes considered to be an initialism that is pronounced as a word (e.g. NATO), as distinct from an initialism pronounced as a string of individual letters (e.g. "UN" for United Nations). In this document the term acronym includes initialisms. The term word acronym can be used to refer to acronyms which are not initialisms.

Do not edit-war over these terms. When using more precise terms like word acronym and initialism, please link to Acronym § Nomenclature, where they are explained for readers.

• Capitalisation: Some acronyms are written with all capital letters, some with a mixture of capitals and lower-case letters and some are written as common nouns (e.g., laser). Acronyms of letters that are pronounced individually (initialisms) are always written in capitals (e.g., FBI). (For more guidance on the capitalisation of acronyms, see Wikipedia:Manual of Style/Capital letters#Acronyms.)
• Spacing: The letters of acronyms should not be spaced.
• Plurals: Plural acronyms are written with a lower-case s after the abbreviation, without an apostrophe, unless full points are used between the letters (e.g. ABCs or A.B.C.'s). Note that Wikipedia generally avoids using full point in upper-case acronyms.
• Emphasis: Do not apply special style, such as SMALL CAPS, to acronyms. Do not apply italics, boldfacing, underlining, or other highlighting to the letters in the expansion of an acronym that correspond to the letters in the acronym, as in BX (Base Exchange). It is not necessary to state that an acronym is an acronym. Our readers should not be browbeaten with the obvious.

If there is an article about the subject of an acronym (e.g. NATO), then other articles should use the same style (capitalisation and punctuation) as that main article. If no such article exists, then style should be resolved by considering consistent usage in source material.

Unless specified in the "Exceptions" section below, an acronym should be written out in full for the first time, followed by the abbreviation in parentheses, e.g. maximum transmission unit (MTU) if it is used again in the article. Common exceptions are post-nominal initials, because writing them out in full would cause clutter, or for something most commonly known by its acronym, in which case the expansion can be omitted (except in the lead of its own article) or be in parentheses—e.g. according to the CIA (Central Intelligence Agency).

To save space in small spaces (see § Use sourceable abbreviations), acronyms do not need to be written out in full. When not written out in full on the first use, an acronym should be linked. An unambiguous acronym can be linked as-is, but an ambiguous acronym should be linked to its expansion. Upon re-use in a long article, the template {{abbr}} can be used to provide a mouse-over tooltip, giving the meaning of the acronym again without having to redundantly link or spell it out again. The template inserts a <abbr> tag into the page's HTML. Example: {{abbr|CIA|Central Intelligence Agency}}, giving: CIA. (This mouse-over will not work on mobile devices, which represent the majority of Wikimedia traffic.^[1])

For partial acronyms formed using the now-rare convention of including whole short words in them, do not blindly "normalise" them to typical current style, but write each as found in the majority of modern reliable sources. Examples: "Commander-in-Chief" is generally abbreviated CinC on its own, but may appear in all-caps when used in a longer acronym (especially a US government one) like CINCFLEET and CINCAIR. The Billiard Association of America was known as BA of A; while this should not be written as unsourceable variations like BAofA or BAA, the awkwardness of the abbreviation to modern eyes can be reduced by replacing the full-width spaces with thin-space characters: BA{{thinsp}}of{{thinsp}}A or BA of A gives BA of A, which better groups the letters into a unit.

Ship name prefixes like HMS and USS should not be written out in full.

Abbreviations for time zones (e.g. GMT and UTC) should not be written out in full after times.

For these commonly-referred-to entities, the name does not need to be written out in full on first use, nor provided on first use in parentheses after the full name if written out.

Acronyms in this table do not need to be written out in full upon first use, except in their own articles or where not doing so would cause ambiguity.

Acronyms should be used in a page name if the subject is known primarily by its abbreviation and that abbreviation is primarily associated with the subject (e.g. NASA; in contrast, consensus has rejected moving Central Intelligence Agency to its acronym, in view of arguments that the full name is used in professional and academic publications). In general, if readers somewhat familiar with the subject are likely to only recognise the name by its acronym, then the acronym should be used as a title. If the acronym and the full name are both in common use, both pages should exist, with one (usually the abbreviation) redirecting to the other or being a disambiguation page.

One general exception to this rule deals with our strong preference for natural disambiguation. Many acronyms are used for several things; naming a page with the full name helps to avoid clashes. For instance, multiple TV/radio broadcasting companies share the initials ABC; even though some may be far better known by that acronym, our articles on those companies are found at, for example, American Broadcasting Company rather than ABC (American TV network).^[a] A useful test to determine what an abbreviation usually refers to can be done by checking Acronym Finder or Abbreviations.com and finding the relative usage. If it is found that a particular subject is overwhelmingly denoted by an unambiguous acronym, the article title on that subject can be expressed as the acronym and a disambiguation page can be used for the other subjects.

In many cases, no decision is necessary because a given acronym has several expansions, none of which is the most prominent. Under such circumstances, an article should be named with the spelled-out phrase and the acronym should be a disambiguation page providing descriptive links to all of them. See, for example, AJAR, which disambiguates between African Journal of AIDS Research and Australian Journal of Agricultural Research. A title like AJAR (African journal) should be avoided if at all possible.

To save space, acronyms should be used as disambiguators, when necessary. For example, "Georgia (U.S. state)", "Great Northern Railway (U.S.)" and "Labour Party (UK)". The abbreviations are preferred over United States and United Kingdom, for brevity. In running text, more natural wording is often better ("the US state of Georgia", "US-based Great Northern Railway", "the Labour Party of the UK"), though this may depend on context.

To help navigation to article titles with these United States abbreviations, please create a redirect that contains (U.S.) or (US) as needed. For example, "Great Northern Railway (US)" should redirect to "Great Northern Railway (U.S.)" (or the other way around). Wikipedia does not use USA, except in proper names and in standardized codes (e.g. FIFA's) that use it.

A contraction is an abbreviation of one or more words that has some or all of the middle letters removed but retains the first and final letters (e.g. Mr and aren't). Missing letters are replaced by an apostrophe in most multiple-word contractions. Contractions such as aren't should not be used in Wikipedia, except in quoted material; use the full wording (e.g., are not) instead. The contraction o'clock is an exception, as it is standard in all registers of writing. Certain placenames may use particular contractions (see § Special considerations, below).

Per the guideline on titles of people, prefix titles such as Mr, Dr, and Prof. should not be used. Prefixes of royalty and nobility often should be used, but not in abbreviated form. (For article titles, see: Wikipedia:Naming conventions (people) § Titles and styles; and Wikipedia:Naming conventions (royalty and nobility).)

For initials in biographical names, see Wikipedia:Manual of Style/Biographies § Initials.

A shortening is an abbreviation formed by removing at least the last letter of a word (e.g. etc. and rhino), and sometimes also containing letters not present in the full form (e.g. bike). As a general rule, use a full point after a shortening that only exists in writing (e.g. etc.) but not for a shortening that is used in speech (e.g. rhino). In general, a full form is as acceptable as a shortened form, but there are exceptions e.g. etc. should be used over et cetera. Uncommon, non-obvious shortenings should be explained or linked on first use on a page.

Outside of prose, trad. and arr. may be used in songwriting credits to save space. On first usage, use {{trad.}} and {{arr.}}, which will display a mouse-over tooltip expanding the abbreviation. Similarly, feat. for featuring has become common in modern music, and may appear in song or album credits, or in actual song titles, depending on the specific work. The template {{feat.}} exists for it. Avoid using the ambiguous hyper-abbreviation ft. except in verbatim material such as titles and quotations.

• The ampersand (&), a replacement for the word and, should only be used in small spaces such as tables and infoboxes, but, preferably, should be avoided even there. However, it is common in many trademarks and titles of published works, and should be retained when found in them.

Do not use Unicode characters that put an abbreviation into a single character (unless the character itself is the subject of the text), e.g.: №, ㋏, ㎇, ㉐, Ⅶ, ℅, ™︎. These are not all well-supported in Western fonts. This does not apply to currency symbols, such as ₨ and ₠. For more comprehensive lists, see Ligatures in Unicode, Letterlike Symbols, CJK Compatibility, Enclosed CJK Letters and Months, and Enclosed Alphanumeric Supplement.

As with other non-English vocabulary, Latin-language terms should be tagged as such using the {{lang|la|...}} template, which automatically italicises the text. This includes Latin abbreviations, except those that are commonly used in English, such as AD, c., e.g., etc., i.e., and several others found in the table above. Do not use &c. in place of etc.

Other Latinisms that are considered English vocabulary and therefore are not tagged or italicised include versus and per cent. If in doubt, consult reliable dictionaries and follow their lead.

Wikipedia has found it both practical and efficient to use the following abbreviations in tight quarters such as citations, tables, and lists. Most should be replaced, in regular running text, by unabbreviated expansions or essentially synonymous plain English (that is for i.e., namely for viz., and so on), when space permits or when the material would be clearer to more readers. A common rule of thumb regarding i.e. and e.g. is that they are best used in parentheticals rather than in the main flow of a sentence. Versions of non-acronym abbreviations that do not end in full points (periods) are more common in British than North American English and are always^[b] abbreviations that compress a word while retaining its first and last letters (i.e., contractions: Dr, St, Revd) rather than truncation abbreviations (Prof., Co.). That said, US military ranks are often abbreviated without this punctuation (though they should not be given in all-caps, despite that style existing "in the wild" in some publications).

• Postal codes and abbreviations of place names—e.g., Calif. (California), TX (Texas), Yorks. (Yorkshire)—should not be used to stand for the full names in normal text. They can be used in tables when space is tight but should be marked up with {{abbr}} template on first occurrence. They should not be used in infoboxes. An exception is Washington, D.C., which has been conventionally called so, for reasons of clarity, since long before postal codes were invented. "Washington, D.C.", or "Washington, DC", may be used in tables whether or not other state postal codes appear. Never use "Washington D.C." (without a comma).
• Saint (or Sainte) versus the St and St. (or Ste.) abbreviations in placenames should follow the most common rendering found in reliable sources for that particular locale; this will most often match the official name of the place.

• Wikipedia:Manual of Style § Acronyms and abbreviations
• Wikipedia:Manual of Style/Capital letters § Acronyms
• American and British English differences § Punctuation
• Wikipedia:Edit summary legend
• Wikipedia:Naming conventions (aircraft)
• Wikipedia:Naming conventions (ships)