Acronym

===Case===
====All-caps style====
The most common [[capitalization]] scheme seen with acronyms is all-uppercase ([[all caps]]). [[Small caps]] are sometimes used to make the run of capital letters seem less jarring to the reader. For example, the style of some American publications, including the ''[[Atlantic Monthly]]'' and ''[[USA Today]]'', is to use small caps for acronyms longer than three letters;{{Citation needed|date=August 2007}} thus "U.S." and "[[Franklin D. Roosevelt|FDR]]" in normal caps, but "{{smallcaps|nato}}" in small caps. The acronyms "[[Anno Domini|AD]]" and "[[Before Christ|BC]]" are often smallcapped as well, as in: "From {{nowrap|4004 {{smallcaps|bc}} to {{smallcaps|ad}} 525}}".

====Normal case and anacronyms<span class="anchor" id="Anacronym"></span>====
Where an acronym has linguistically taken on an identity as regular word, the acronym may use normal case rules, e.g. it would appear generally in lower case, but with an initial capital when starting a sentence or when in a title. Once knowledge of the words underlying such an acronym has faded from common recall, the acronym may be termed an '''anacronym'''.<ref>{{ShorterOxfordEnglishDictionary}}</ref> Examples of anacronyms are the words "[[scuba set|scuba]]", "[[radar]]", and "[[laser]]".  The word "an''acro''nym" should not be confused with the word "[[Misnomer#Anachronym|an''achro''nym]]", which is a type of misnomer.

====Mixed-case variant====
Words derived from an acronym by affixing are typically expressed in mixed case, so the root acronym is clear. For example, "pre-WWII politics", "post-NATO world", "[[DNase]]". In some cases a derived acronym may also be expressed in mixed case. For example, "[[messenger RNA]]" and "[[transfer RNA]]" become "mRNA" and "tRNA".

====Pronunciation-dependent style and case====
Some publications choose to capitalize only the first letter of acronyms, reserving all-caps styling for initialisms, writing the pronounced acronyms "Nato" and "Aids" in mixed case, but the initialisms "USA" and "FBI" in all caps. For example, this is the style used in ''[[The Guardian]]'',<ref>{{Cite news |url= https://www.theguardian.com/styleguide |title=Styleguide |work=[[The Guardian]] |location=London |date=December 19, 2008 |quote=Use all capitals if an abbreviation is pronounced as the individual letters (an initialism): BBC, CEO, US, VAT, etc; if it is an acronym (pronounced as a word) spell out with initial capital, eg Nasa, Nato, Unicef, unless it can be considered to have entered the language as an everyday word, such as [[awol]], [[laser]] and, more recently, [[asbo]], [[pin number]] and [[sim card]]. Note that [[pdf]] and [[public limited company|plc]] are lowercase.}}</ref> and ''[[BBC News]]'' typically edits to this style (though its official style guide, dating from 2003, still recommends all-caps<ref>{{Cite news|url= http://www.bbctraining.com/pdfs/newsstyleguide.pdf |title=BBC News Style Guide |work=BBCTraining.com |publisher=[[BBC]] |archive-url= https://web.archive.org/web/20110707214856/http://www.bbctraining.com/pdfs/newsStyleGuide.pdf |archive-date=July 7, 2011}}</ref>). The logic of this style is that the pronunciation is reflected graphically by the capitalization scheme. However, it conflicts with conventional English usage of first-letter upper-casing as a marker of proper names in many cases; e.g. ''AIDS'' stands for ''acquired immuno-deficiency syndrome'' which is not a proper name, while ''Aids'' is in the style of one.

Some style manuals also base the letters' [[Letter case|case]] on their number. ''[[The New York Times]]'', for example, keeps "NATO" in all capitals (while several guides in the British press may render it "Nato"), but uses lower case in "[[United Nations Children's Fund|Unicef]]" (from "United Nations International Children's Emergency Fund") because it is more than four letters, and to style it in caps might look ungainly (flirting with the appearance of "shouting capitals").