Acronym

===Punctuation===
====Showing the ellipsis of letters====
In English, abbreviations have previously been marked by a wide variety of [[English punctuation|punctuation]]. Obsolete forms include using an [[overbar]] or [[colon (punctuation)|colon]] to show the [[ellipsis]] of letters following the initial part. The [[forward slash]] is still common in many dialects for some fixed expressions{{mdash}}such as ''w/'' for "with" or ''A/C'' for "[[air conditioning]]"{{mdash}}while only infrequently being used to abbreviate new terms. The [[apostrophe]] is common for [[Contraction (grammar)#English|grammatical contractions]] (e.g. ''don't'', ''[[y'all]]'', and ''[[ain't]]'') and for contractions marking unusual pronunciations (e.g. ''a'ight'', ''cap'n'', and ''fo'c'sle'' for "all right", "captain", and "forecastle"). By the early twentieth century, it was standard to use a [[full stop|full stop/period/point]], especially in the cases of initialisms and acronyms. Previously, especially for [[Latin abbreviations]], this was done with a full space between every full word (e.g. {{lang|la|A. D.}}, {{lang|la|i. e.}}, and {{lang|la|e. g.}} for "[[Anno Domini]]", "[[id est]]", and "[[exempli gratia]]"). This even included punctuation after both [[Roman numerals|Roman]] and [[Arabic numerals]] to indicate their use in place of the full names of each number (e.g. ''LII.'' or ''52.'' in place of "fifty-two" and "1/4." or "1./4." to indicate "one-fourth"). Both conventions have fallen out of common use in all dialects of English, except in places where an Arabic [[decimal number|decimal]] includes a medial [[decimal point]].

Particularly in [[British English|British]] and [[Commonwealth English]], all such punctuation marking acronyms and other capitalized abbreviations is now uncommon and considered either unnecessary or incorrect. The presence of all-capital letters is now thought sufficient to indicate the nature of the ''[[United Kingdom|UK]]'', the ''[[European Union|EU]]'', and the ''[[United Nations|UN]]''. Forms such as ''the U.S.A.'' for "the [[United States of America]]" are now considered to indicate [[American English|American]] or [[North American English]]. Even within those dialects, such punctuation is becoming increasingly uncommon.<ref>[[Oxford English Dictionary]]: ''initialism''. "Globe & Mail (Toronto) 22 May 10/4 Americanization has also largely done away with periods in acronyms and initialisms."</ref>

=====Ellipsis-is-understood style=====
Some [[style guide]]s, such as that of the [[BBC]], no longer require punctuation to show [[ellipsis]]; some even proscribe it. [[Larry Trask]], American author of ''The [[Penguin Books|Penguin]] Guide to Punctuation'', states categorically that, in [[British English]], "this tiresome and unnecessary practice is now obsolete."<ref>{{cite web |url= http://www.informatics.susx.ac.uk/doc/punctuation/node28.html |title=Abbreviations |publisher=Informatics.Susx.ac.uk |access-date=September 16, 2010 |archive-url= https://web.archive.org/web/20070410113359/http://www.informatics.susx.ac.uk/doc/punctuation/node28.html |archive-date=April 10, 2007 }}</ref>

=====Pronunciation-dependent style and periods=====
Nevertheless, some influential [[style guide]]s, many of them [[American English|American]], still require periods in certain instances. For example, ''[[The New York Times Manual of Style and Usage]]'' recommends following each segment with a period when the letters are pronounced individually, as in "[[KGB|K.G.B.]]", but not when pronounced as a word, as in "[[NATO]]".<ref name = "NY Times">{{Cite news |url= https://www.nytimes.com/2004/02/07/opinion/secret-obsessions-at-the-top.html |access-date=October 10, 2015 |title=Secret Obsessions at the Top |first=Nicholas D. |last=Kristoff |work=[[The New York Times]] |date=February 7, 2004 |archive-url= https://web.archive.org/web/20150528024321/http://www.nytimes.com/2004/02/07/opinion/secret-obsessions-at-the-top.html |archive-date=May 28, 2015 |url-status=live}}</ref> The logic of this style is that the pronunciation is reflected graphically by the punctuation scheme.

=====Other conventions=====
When a multiple-letter abbreviation is formed from a single word, periods are in general not used, although they may be common in informal usage. "TV", for example, may stand for a ''single'' word ("television" or "transvestite", for instance), and is in general spelled without punctuation (except in the plural). Although "PS" stands for the single English word "[[postscript]]" or the Latin ''postscriptum'', it is often spelled with periods ("P.S.") as if parsed as Latin ''post scriptum'' instead.

The [[slash (punctuation)|slash]] ('/', or ''solidus'') is sometimes used to separate the letters in an acronym, as in "N/A" ("not applicable, not available") and "c/o" ("care of").

Inconveniently long words used frequently in related contexts can be represented according to their letter count as a [[numeronym]]. For example, "i18n" abbreviates "[[internationalization]]", a computer-science term for adapting software for worldwide use. The "18" represents the 18 letters that come between the first and the last in "internationalization". "Localization" can be abbreviated "l10n", "[[multilingualization]]" "m17n", and "[[accessibility]]" "a11y". In addition to the use of a specific number replacing that many letters, the more general "x" can be used to replace an unspecified number of letters. Examples include "Crxn" for "crystallization" and the series familiar to physicians for [[medical history|history]], [[medical diagnosis|diagnosis]], and [[therapy|treatment]] ("hx", "dx", "tx"). Terms relating to a command structure may also sometimes use this formatting, for example gold, silver, and bronze levels of command in UK policing being referred to as Gx, Sx, and Bx.

====Representing plurals and possessives====
There is a question about how to pluralize acronyms. Often a writer will add an 's' following an apostrophe, as in "PC's". However, [[Kate L. Turabian]]'s ''[[A Manual for Writers of Research Papers, Theses, and Dissertations]]'', writing about style in academic writings,<ref name="Chicago">{{cite book |last1=Turabian |first1=Kate L. |author1-link=Kate L. Turabian |last2=Booth |first2=Wayne C. |last3=Colomb |first3=Gregory G. |last4=Williams |first4=Joseph M. |title=[[A Manual for Writers of Research Papers, Theses, and Dissertations]] |edition=7th |date=2007 |at=§&nbsp;20.1.2 |publisher=[[University of Chicago Press]] |isbn=978-0-226-82337-9}}</ref> allows for an apostrophe to form plural acronyms "only when an abbreviation contains internal periods or both capital and lowercase letters". Turabian would therefore prefer "DVDs" and "URLs" but "Ph.D.'s". The style guides of the [[Modern Language Association]]<ref name="MLA">{{cite book |publisher=[[Modern Language Association]] |title=[[MLA Handbook]] for Writers of Research Papers |edition=7th |date=2009 |at=§&nbsp;3.2.7.g}}</ref> and [[American Psychological Association]]<ref name="APA">{{cite book |title=Publication Manual of the American Psychological Association |edition=5th |date=2001 |at=§&nbsp;3.28 |publisher=[[American Psychological Association]]}}</ref><ref name=autogenerated1>{{cite book |title=[[Publication Manual of the American Psychological Association]] |edition=6th |date=2010 |at=§&nbsp;4.29 |publisher=[[American Psychological Association]]}}</ref> prohibit apostrophes from being used to pluralize acronyms regardless of periods (so "compact discs" would be "CDs" or "C.D.s"), whereas ''[[The New York Times Manual of Style and Usage]]'' requires an apostrophe when pluralizing all abbreviations regardless of periods (preferring "PC's, TV's and VCR's").<ref>{{cite book |last1=Siegal |first1=Allan M. |author1-link=Allan M. Siegal |last2=Connolly |first2=William G. |author2-link=William G. Connolly |title=[[The New York Times Manual of Style and Usage]] |page=[https://www.google.com/books/edition/The_New_York_Times_Manual_of_Style_and_U/CnwIVkAQgFwC?hl=en&gbpv=1&pg=PA263 263] |via=Google Books |publisher=Three Rivers Press |date=1999}}</ref>

Possessive plurals that also include apostrophes for mere pluralization and periods appear especially complex: for example, "the C.D.'s' labels" (the labels of the compact discs). In some instances, however, an apostrophe may increase clarity: for example, if the final letter of an abbreviation is "S", as in "SOS's" (although abbreviations ending with S can also take "-es", e.g. "SOSes"), or when pluralizing an abbreviation that has periods.<ref>{{cite web |url= http://www.writersblock.ca/tips/monthtip/tipmar96.htm |title=Writer's Block&nbsp;– Writing Tips&nbsp;– Plural and Possessive Abbreviations |publisher=WritersBlock.ca |access-date=September 16, 2010 |archive-url= https://web.archive.org/web/20100726124408/http://www.writersblock.ca/tips/monthtip/tipmar96.htm |archive-date=July 26, 2010}}</ref><ref>{{cite web |url= http://www.editfast.com/english/grammar/apostrophes/apostrophe_plurals.htm |title=EditFast Grammar Resource: Apostrophes: Forming Plurals |publisher=Editfast.com |access-date=September 16, 2010 |archive-url= https://web.archive.org/web/20101027001351/http://editfast.com/english/grammar/apostrophes/apostrophe_plurals.htm |archive-date=October 27, 2010 }}</ref>

A particularly rich source of options arises when the plural of an acronym would normally be indicated in a word other than the final word if spelled out in full. A classic example is "Member of Parliament", which in plural is "Members of Parliament". It is possible then to abbreviate this as "M's P", which was fairly common in mid-twentieth-century Australian news writing<ref>{{cite web |url= https://trove.nla.gov.au/work/26924909 |title=Libraries Australia&nbsp;– T.H. McWilliam, Charles Kingsford Smith, Prime Minister of New Zealand Joseph Coates, Charles Ulm and H.A. Litchfield in front row with Members of Parliament on steps of Parliament House, Wellington, New Zealand, September 1928 |at=Notes |work=NLA.gov.au |publisher=[[National Library of Australia]] |access-date=September 16, 2010 |archive-url= https://web.archive.org/web/20080622132412/http://nla.gov.au/anbd.bib-an41354070 |archive-date=June 22, 2008 |url-status= live}}</ref><ref>{{cite web |first=Robin |last=Hyde |url= https://nzetc.victoria.ac.nz/tm/scholarly/tei-HydJour-t1-body-d3.html |title=Chapter III.&nbsp;— The House is in Session |publisher=NZETC |access-date=September 16, 2010 |archive-url= https://web.archive.org/web/20110430012333/https://nzetc.victoria.ac.nz/tm/scholarly/tei-HydJour-t1-body-d3.html |archive-date=April 30, 2011 |url-status=live}}</ref> (or similar<ref>{{cite web |url= http://www.middlemiss.org/lit/authors/denniscj/backblockother/underpartyplan.html |title=Under the party plan |first=C. J. |last=Dennis |author-link=C. J. Dennis |work=[[The Bulletin (Australian periodical)|The Bulletin]] |date=January 18, 1912 |page=43 |via=Middlemiss.org |access-date=September 16, 2010 |archive-url= https://web.archive.org/web/20100822175445/http://www.middlemiss.org/lit/authors/denniscj/backblockother/underpartyplan.html |archive-date=August 22, 2010 |url-status=live}}</ref>), and used by former Australian Prime Minister [[Ben Chifley]].<ref>{{cite news |url= https://trove.nla.gov.au/newspaper/page/5605107 |via=Trove.NLA.gov.au |title=M's.P. Suffer Loss and Insecurity |date=December 2, 1948 |work=[[Townsville Bulletin|Townsville Daily Bulletin]] |page=1}}</ref><ref>{{cite news |url= https://trove.nla.gov.au/newspaper/article/27755397 |date=October 14, 1948 |title=Prime Minister Asserts M's.P. Have No Immunity from 'Official Approaches' |work=[[The Mercury (Hobart)|The Mercury]] |page=2 |via=Trove.NLA.gov.au}}</ref><ref>{{cite web |url= http://www.electricscotland.com/history/australia/melbourne11.htm |title=The Royal Caledonian Society of Melbourne |via=ElectricScotland.com |access-date=January 21, 2013 |archive-url= https://web.archive.org/web/20120715091217/http://www.electricscotland.com/history/australia/melbourne11.htm |archive-date=July 15, 2012 |url-status=live}}</ref> This usage is less common than forms with "s" at the end, such as "MPs", and may appear dated or pedantic. In common usage, therefore, "weapons of mass destruction" becomes "WMDs", "prisoners of war" becomes "POWs", and "runs batted in" becomes "RBIs".<ref>{{cite book |last=Garner |first=Bryan |author-link=Bryan Garner |title=[[Garner's Modern American Usage]] |date=August 27, 2009 |publisher=Oxford University Press |location=Oxford / New York |isbn=978-0-19-538275-4 |page=638}}</ref>

The argument that acronyms should have no different plural form (for example, "If ''D'' can stand for ''disc'', it can also stand for ''discs''") is in general disregarded because of the practicality in distinguishing singulars and plurals. This is not the case, however, when the abbreviation is understood to describe a plural noun already: For example, "U.S." is short for "United States", but not "United State". In this case, the options for making a possessive form of an abbreviation that is already in its plural form without a final "s" may seem awkward: for example, "U.S.", "U.S.'s", etc. In such instances, possessive abbreviations are often forgone in favor of simple [[adjective|attributive]] usage (for example, "the U.S. economy") or expanding the abbreviation to its full form and ''then'' making the possessive (for example, "the United States' economy"). On the other hand, in speech, the pronunciation "United States's" is sometimes used.

Abbreviations that come from single, rather than multiple, words – such as "TV" ("television") – are usually pluralized without apostrophes ("two TVs"); most writers feel that the apostrophe should be reserved for the possessive ("the TV's antenna").

{{anchor|pp|PP|pP|Pp|page|pages}} In some languages, the convention of doubling the letters in the acronym is used to indicate plural words: for example, the Spanish {{lang|es|EE.UU.}}, for {{lang|es|Estados Unidos}} ('United States'). This old convention is still followed for a limited number of English abbreviations, such as ''SS.'' for ''Saints'', ''pp.'' for the Latin plural of 'pages', {{lang|la|paginae}}, or ''mss.'' for ''manuscripts''.

{{further|English possessive}}