Editing Abbreviation (section)

=== Periods ===
[[File:“To Penna. R.R. Station”.jpg|thumb|Sign in New York City subway, reading "Penna." for Penn''sylvani''a, showing American style of including the period even for contractions]]
A period (a.k.a. full stop) is sometimes used to signify abbreviation, but opinion is divided as to when and if this convention is best practice.

According to [[Hart's Rules]], a word shortened by dropping letters from the end terminates with a period, whereas a word shorted by dropping letters from the middle does not.<ref name=harts/>{{rp|p167–170}} [[Fowler's Modern English Usage]] says a period is used for both of these shortened forms, but recommends against this practice: advising it only for end-shortened words and lower-case initialisms; not for middle-shortened words and upper-case initialisms.<ref>{{cite book|title=Pocket Fowler's Modern English Usage|edition=2nd|editor-first=Robert|editor-last=Allen|publisher=Oxford University Press|date=2008|isbn=9780191727078|contribution=Full stop}}</ref>

{| class="wikitable"
|-
!Full form
!Shortening
!Short form
!Source
|-
|[[Doctor (title)|Doctor]]
|mid
|Dr
|D——r
|-
|[[Professor]]
|end
|Prof.
|Prof...
|-
|[[Reverend|The Reverend]]
|end
|Rev.
|Rev...
|-
|[[Reverend|The Reverend]]
|mid
|Revd
|Rev——d
|-
|[[The Right Honourable]]
|mid and end
|Rt Hon.
|R——t Hon...
|}

Some British style guides, such as for [[The Guardian]] and [[The Economist]], disallow periods for all abbreviations.<ref>{{Cite news |date=2021-04-30 |title=Guardian and Observer style guide: A |language=en-GB |work=The Guardian |url=https://www.theguardian.com/guardian-observer-style-guide-a |access-date=2023-04-22 |issn=0261-3077 |quote="Do not use full points in abbreviations, or spaces between initials, including those in proper names: IMF, mph, eg, 4am, M&S, No 10, AN Wilson, WH Smith, etc." }}</ref><ref>{{cite book |author=The Economist |title=Style guide |date=2005 |publisher=Profile Books |edition=9th |isbn=978-1-84765-030-6 |location=London |oclc=236346040 |page=117 |quote=Do not use full stops in abbreviations... }}</ref>

In [[American English]], the period is usually included regardless of whether or not it is a contraction, e.g. ''Dr.'' or ''Mrs.'' In some cases, periods are optional, as in either ''US'' or ''U.S.'' for ''United States'', ''EU'' or ''E.U.'' for ''European Union'', and ''UN'' or ''U.N.'' for ''United Nations''. There are some house styles, however—American ones included—that remove the periods from almost all abbreviations. For example:
* The U.S. [[Manual on Uniform Traffic Control Devices]] advises that periods should not be used with abbreviations on road signs, except for cardinal directions as part of a destination name. (For example, ''"Northwest Blvd"'', ''"W. Jefferson"'', and ''"PED XING"'' all follow this recommendation.) 
* [[AMA Manual of Style|AMA style]], used in many [[medical journal]]s, uses no periods in abbreviations or acronyms, with almost no exceptions. Thus [[exempli gratia|eg]], [[id est|ie]], [[wikt:versus|vs]], [[et al.]], [[Doctor (title)|Dr]], [[Mr.|Mr]], [[magnetic resonance imaging|MRI]], [[intensive care unit|ICU]], and hundreds of others contain no periods. The only exceptions are {{char|No.}} (an abbreviation of [[Numero sign|Numero]], Number), to avoid confusion with the word "[[Yes and no|No]]"; initials within persons' names (such as "George R. Smith"); and "St." within persons' names when the person prefers it (such as "Emily R. St. Clair") (but not in city names such as ''St Louis'' or ''St Paul'').

Acronyms that were originally capitalized (with or without periods) but have since entered the vocabulary as generic words are no longer written with capital letters nor with any periods. Examples are [[sonar]], [[radar]], [[lidar]], [[laser]], [[SNAFU|snafu]], and [[Scuba set|scuba]].

When an abbreviation appears at the end of a sentence, only one period is used: ''The capital of the United States is Washington, D.C.''

In the past, some initialisms were styled with a period after each letter and a space between each pair. For example, ''U.&nbsp;S.'', but today this is typically ''US''.