Editing At sign (section)

=== Other uses and meanings ===
{{More citations needed|date=November 2021}}
[[File:Atletter.svg|right|thumb|150px|[[Bicameral script|Bicameral]] @ letter as used in the [[Koalib language]].]]
[[File:OCR-A char Commercial At.svg|right|thumb|75px|[[X-SAMPA]] uses an @ as a substitute for [[ə]], which it resembles in some fonts.]]
* In (especially English) scientific and technical literature, @ is used to describe the conditions under which data are valid or a measurement has been made. E.g. the density of saltwater may read ''d'' = 1.050 g/cm<sup>3</sup> @ 15&nbsp;°C (read "at" for @), density of a gas ''d'' = 0.150 g/L @ 20&nbsp;°C, 1 bar, or noise of a car 81&nbsp;dB @ 80&nbsp;km/h (speed).<ref name="getproofed">{{cite web |title=When to Use the At Symbol (@) in Writing |url=https://getproofed.com/writing-tips/when-to-use-the-at-symbol-in-writing/ |access-date=10 November 2021 |date=11 December 2019 |archive-date=10 November 2021 |archive-url=https://web.archive.org/web/20211110171325/https://getproofed.com/writing-tips/when-to-use-the-at-symbol-in-writing/ |url-status=live }}</ref>
*In [[philosophical logic]], '@' is used to denote the actual world (in contrast to non-actual possible worlds).{{citation needed|date=November 2020}} Analogously, a 'designated' world in a [[Kripke semantics|Kripke model]] may be labelled '@'.{{citation needed|date=March 2021}}
* In chemical formulae, @ is used to denote [[Chemical formula#Trapped atoms|trapped atoms]] or molecules.<ref name="YanChai">{{Cite journal |last1=Chai, Yan |last2=Guo, Ting |last3=Jin, Changming |last4=Haufler, Robert E. |last5=Chibante, L. P. Felipe |last6=Fure, Jan |last7=Wang, Lihong |last8=Alford, J. Michael |last9=Smalley, Richard E. |year=1991 |title=Fullerenes wlth Metals Inside |journal=Journal of Physical Chemistry |volume=95 |issue=20 |pages=7564–7568 |doi=10.1021/j100173a002}}</ref> For instance, La@C<sub>60</sub> means [[lanthanum]] inside a [[fullerene]] cage. See article [[Endohedral fullerene]] for details.
* In [[Malagasy language|Malagasy]], @ is an informal abbreviation for the prepositional form ''amin'ny''.{{citation needed|date=March 2021}}
* In [[Malay language|Malay]], @ is an informal abbreviation for the word "atau", meaning "or" in English.{{citation needed|date=March 2021}}
* In [[genetics]], @ is the abbreviation for [[locus (genetics)|locus]], as in [[IGL@]] for ''immunoglobulin lambda locus''.<ref>{{cite web |title=IGL immunoglobulin lambda locus [Homo sapiens (human)] |url=https://www.ncbi.nlm.nih.gov/gene?Db=gene&Cmd=ShowDetailView&TermToSearch=3535 |access-date=10 November 2021}}</ref>
* In the [[Koalib language]] of [[Sudan]], @ is used as a letter in [[Arabic]] [[loanwords]]. The [[Unicode Consortium]] rejected a proposal to encode it separately as a letter in [[Unicode]]. [[SIL International]] uses [[Private Use Area]] code points U+F247 and U+F248 for lowercase and capital versions, although they have marked this PUA representation as [[deprecated]] since September 2014.<ref name="SILPUA">Constable, Peter, and Lorna A. Priest (January 17, 2019) [http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&item_id=SILPUAassignments ''SIL Corporate PUA Assignments 5.2a''] {{Webarchive|url=https://web.archive.org/web/20100223081253/http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&item_id=SILPUAassignments |date=2010-02-23 }}. [http://www.sil.org/ SIL International] {{Webarchive|url=https://web.archive.org/web/20071201070851/http://www.sil.org/ |date=2007-12-01 }}. pp. 59–60. Retrieved on July 20, 2020.</ref>
* A [[schwa]], as the actual schwa character "ə" may be difficult to produce on many computers. It is used in this capacity in some [[Comparison of ASCII encodings of the International Phonetic Alphabet|ASCII IPA schemes]], including [[SAMPA]] and [[X-SAMPA]].{{citation needed|date=March 2021}}
* In [[leet]] it may substitute for the letter "A".{{citation needed|date=March 2021}}
* It is frequently used in typing and [[text messaging]] as an abbreviation for "at".<ref>{{cite book |last1=Crystal |first1=David |title=Txtng: the gr8 db8 |date=2008 |publisher=New York: Oxford University Press |isbn=978-0-19-162340-0 |pages=131–137 |url=https://books.google.com/books?id=pKBnEGwmtZoC&pg=PA131 |access-date=2021-11-10 |archive-date=2021-11-10 |archive-url=https://web.archive.org/web/20211110182712/https://books.google.com/books?id=pKBnEGwmtZoC&pg=PA131 |url-status=live }}</ref><ref name="getproofed" />
* In Portugal it may be used in typing and text messaging with the meaning "[[french kiss]]" (''linguado'').{{citation needed|date=March 2021}}
* In online discourse, @ is used by some [[anarchists]] as a substitute for the traditional [[circle-A]].{{citation needed|date=March 2021}}
* Algebraic notation for the [[Crazyhouse]] chess variant: An @ between a piece and a square denotes a piece dropped onto that square from the player's reserve.<ref name="ficshelp">{{cite web|date=2008-02-28|title=crazyhouse|url=http://www.freechess.org/Help/HelpFiles/crazyhouse.html|url-status=live|archive-url=https://web.archive.org/web/20140416133658/http://www.freechess.org/Help/HelpFiles/crazyhouse.html|archive-date=2014-04-16|access-date=2014-04-17|work=FICS Help|publisher=[[Free Internet Chess Server]]}}</ref>
* In many [[roguelike]] games, @ is used to represent the player character.
* In Spain and Portugal, the ''[[Arroba]]'', abbreviated using the @ sign, is a customary unit of weight, mass or volume. The name ''arroba'' is used in both countries for the @ sign more generally.