Editing At sign (section)

== Modern use ==

=== Commercial usage ===
In contemporary English usage, @ is a commercial symbol, meaning ''at'' and ''at the rate of'' or ''at the price of''. It has rarely been used in financial ledgers, and is not used in standard [[typography]].<ref>[[Bringhurst, Robert]] (2002). ''[[The Elements of Typographic Style]]'' (version 2.5), p.272. Vancouver: Hartley & Marks. {{ISBN|0-88179-133-4}}.</ref>

=== Trademark ===
In 2012, "@" was registered as a [[trademark]] with the German Patent and Trade Mark Office.<ref>German Patent and Trademark Office, registration number [https://register.dpma.de/DPMAregister/marke/register/3020120383386/DE?lang=en 302012038338] {{Webarchive|url=https://web.archive.org/web/20121102053509/http://register.dpma.de/DPMAregister/marke/register/3020120383386/DE?lang=en |date=2012-11-02 }}.</ref> A cancellation request was filed in 2013, and the cancellation was ultimately confirmed by the German Federal Patent Court in 2017.<ref>Bundespatentgericht, decision of 22 February 2017, no. 26 W (pat) 44/14 ([http://juris.bundespatentgericht.de/cgi-bin/rechtsprechung/document.py?Gericht=bpatg&Art=en&Datum=Aktuell&Sort=12288&nr=29334&pos=1&anz=162&Blank=1.pdf online] {{Webarchive|url=https://web.archive.org/web/20190322140609/http://juris.bundespatentgericht.de/cgi-bin/rechtsprechung/document.py?Gericht=bpatg&Art=en&Datum=Aktuell&Sort=12288&nr=29334&pos=1&anz=162&Blank=1.pdf |date=2019-03-22 }}).</ref>

=== Email addresses ===
A common contemporary use of @ is in [[email address]]es (using the [[SMTP]] system), as in <code>jdoe@example.com</code> (the user <code>jdoe</code> located ''at'' the domain <code>example.com</code>). [[Ray Tomlinson]] of [[BBN Technologies]] is credited for having introduced this usage in 1971.<ref name=asperand /><ref>{{Cite web |last=Ray Tomlinson |author-link=Ray Tomlinson |title=The First Email |url=http://openmap.bbn.com/~tomlinso/ray/firstemailframe.html |url-status=live |archive-url=https://web.archive.org/web/20060506003539/http://openmap.bbn.com/~tomlinso/ray/firstemailframe.html |archive-date=2006-05-06 |publisher=[[BBN Technologies]]}}</ref> This idea of the symbol representing ''located at'' in the form <code>user@host</code> is also seen in other tools and protocols; for example, the [[Unix shell]] command <code>ssh jdoe@example.net</code> tries to establish an [[ssh]] connection to the computer with the [[hostname]] <code>example.net</code> using the username <code>jdoe</code>.

On web pages, organizations often obscure the email addresses of their members or employees by omitting the @. This practice, known as [[address munging]], attempts to make the email addresses less vulnerable to spam programs that scan the internet for them.

=== Social media ===
{{Further|Mention (blogging)}}
On some social media platforms and forums, usernames may be prefixed with an @ (in the form <code>@johndoe</code>); this type of username is frequently referred to as a "[[User (computing)|handle]]".{{citation needed|date=November 2022}}

On online forums without [[threaded discussion]]s, @ is commonly used to denote a reply; for instance: <code>@Jane</code> to respond to a comment Jane made earlier. Similarly, in some cases, @ is used for "attention" in email messages originally sent to someone else. For example, if an email was sent from Catherine to Steve, but in the body of the email, Catherine wants to make Keirsten aware of something, Catherine will start the line {{code|@Keirsten}} to indicate to Keirsten that the following sentence concerns her.{{citation needed|date=November 2022}} This also helps with mobile email users who might not see bold or color in email.

In [[microblogging]] (such as on [[Twitter]], [[GNU social]]- and [[ActivityPub]]-based microblogs), an @ before the user name is used to send publicly readable replies (e.g. <code>@otheruser: Message text here</code>). The blog and client software can automatically interpret these as links to the user in question. When included as part of a person's or company's contact details, an @ symbol followed by a name is normally understood to refer to a Twitter handle. A similar use of the @ symbol was also made available to Facebook users on September 15, 2009.<ref>{{Cite web |title=Tag Friends in Your Status and Posts – Facebook Blog |url=http://blog.facebook.com/blog.php?post=109765592130 |url-status=dead |archive-url=https://web.archive.org/web/20091026120029/http://blog.facebook.com/blog.php?post=109765592130 |archive-date=2009-10-26}}</ref> In [[Internet Relay Chat]] (IRC), it is shown before users' nicknames to denote they have operator status on a channel.

=== Sports usage ===
In [[American English]] the @ can be used to add information about a sporting event. Where opposing sports teams have their names separated by a "v" (for [[wikt:versus|versus]]), the [[Road (sports)|away team]] can be written first – and the normal "v" replaced with @ to convey at which team's home field the game will be played.<ref>For an example, see: http://www.nfl.com/schedules {{Webarchive|url=https://web.archive.org/web/20110623181004/http://www.nfl.com/schedules |date=2011-06-23 }}</ref>{{better source needed|date=February 2024}} This usage is not followed in [[British English]], since conventionally the home team is written first.{{citation needed|date=February 2024}}

=== Computer languages ===
@ is used in various [[programming language]]s and other [[computer language]]s, although there is not a consistent theme to its usage. For example:
* In [[ActionScript]], @ is used in XML parsing and traversal as a string prefix to identify attributes in contrast to child elements.<ref>{{Cite web |title=Operators – Adobe ActionScript® 3 (AS3) API Reference |url=https://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/operators.html#attribute_identifier |access-date=2023-05-12 |website=help.adobe.com |language=en-us |archive-date=2023-05-12 |archive-url=https://web.archive.org/web/20230512112456/https://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/operators.html#attribute_identifier |url-status=live }}</ref>
* In [[Ada (programming language)|Ada]] 2022, @ is the ''target name'' symbol, an abbreviation of the [[Sides of an equation|LHS]] of an assignment; it is used to avoid repetition of potentially long names in assignment statements.<ref>{{Cite web |url=http://www.ada-auth.org/standards/22rm/html/rm-5-2-1.html |title=Ada Reference Manual (Ada 2022). Target Name Symbols |website=ada-auth.org |access-date=2024-07-16}}</ref> For example: <code>A_Very_Long_Variable_Name := A_Very_Long_Variable_Name + 1;</code> is shortened to <code>A_Very_Long_Variable_Name := @ + 1;</code>, increasing readability.
* In [[ALGOL 68]], the @ symbol is ''brief form'' of the '''at''' [[keyword (computer programming)|keyword]]; it is used to change the lower bound of an array. For example: {{code|arrayx[@88]}} refers to an array starting at index 88.<ref>{{Cite journal |last=van Wijngaarden |first=A. |date=1981-08-16 |title=Revised Report of the Algorithmic Language Algol 68 |url=https://dl.acm.org/doi/10.5555/1064084.1064085 |journal=ALGOL Bulletin |issue=Sup 47 |pages=121, 532 |doi= |issn=0084-6198 |access-date=2023-05-12 |archive-date=2023-05-12 |archive-url=https://web.archive.org/web/20230512112455/https://dl.acm.org/doi/10.5555/1064084.1064085 |url-status=live }}</ref>
* In Dyalog [[APL (programming language)|APL]], @ is used as a functional way to modify or replace data '''at''' specific locations in an array.
* In the [[ASP.NET MVC]] [[Microsoft ASP.NET Razor view engine|Razor]] template markup syntax, the @ character denotes the start of code statement blocks or the start of text content.<ref>{{Cite web |last=Phil Haack |title=Razor syntax quick reference |date=6 January 2011 |url=http://haacked.com/archive/2011/01/06/razor-syntax-quick-reference.aspx |access-date=12 January 2013 |archive-date=26 January 2022 |archive-url=https://web.archive.org/web/20220126032007/http://haacked.com/archive/2011/01/06/razor-syntax-quick-reference.aspx/ |url-status=live }}</ref><ref>{{Cite web |title=ASP.NET MVC 3: Razor's @: and &lt;text&gt; syntax |url=https://weblogs.asp.net/scottgu/asp-net-mvc-3-razor-s-and-lt-text-gt-syntax |access-date=2020-04-30 |website=weblogs.asp.net |date=16 December 2010 |language=en-US |archive-date=2020-07-26 |archive-url=https://web.archive.org/web/20200726111727/https://weblogs.asp.net/scottgu/asp-net-mvc-3-razor-s-and-lt-text-gt-syntax |url-status=live }}</ref>
* In [[Assembly language]], @ is sometimes used as a [[dereference operator]].<ref>{{Cite web |title=assembly – @ sign in assembler? – Stack Overflow |url=https://stackoverflow.com/questions/11214675/sign-in-assembler |website=stackoverflow.com |access-date=2021-05-02 |archive-date=2021-10-05 |archive-url=https://web.archive.org/web/20211005220705/https://stackoverflow.com/questions/11214675/sign-in-assembler |url-status=live }}</ref>
* In [[CSS]], @ is used in special statements outside of a CSS block.<ref>{{Cite web |title=At-rules |url=https://developer.mozilla.org/en-US/docs/Web/CSS/At-rule |access-date=2020-04-30 |website=MDN Web Docs |language=en |archive-date=2020-05-05 |archive-url=https://web.archive.org/web/20200505194617/https://developer.mozilla.org/en-US/docs/Web/CSS/At-rule |url-status=live }}</ref>
* In [[C Sharp (programming language)|C#]], it denotes "verbatim strings", where no characters are escaped and two double-quote characters represent a single double-quote.<ref>[http://msdn.microsoft.com/en-us/library/aa691090%28v=vs.71%29.aspx 2.4.4.5 String literals] {{Webarchive|url=https://web.archive.org/web/20120805045534/http://msdn.microsoft.com/en-us/library/aa691090(v=vs.71).aspx |date=2012-08-05 }},</ref> As a prefix it also allows keywords to be used as [[identifier (computer programming)|identifiers]],<ref>{{Cite web |title=2.4.2 Identifiers |url=http://msdn.microsoft.com/en-us/library/aa664670%28v=vs.71%29.aspx |access-date=2012-08-16 |archive-date=2012-08-10 |archive-url=https://web.archive.org/web/20120810204003/http://msdn.microsoft.com/en-us/library/aa664670(v=vs.71).aspx |url-status=live }}</ref> a form of [[Stropping (syntax)|stropping]].
* In [[D (programming language)|D]], it denotes function attributes: like: <code>@safe</code>, <code>@nogc</code>, user defined <code>@('from_user')</code> which can be evaluated at compile time (with <code>__traits</code>) or <code>@property</code> to declare properties, which are functions that can be syntactically treated as if they were fields or variables.<ref>{{Cite web |title=Attributes – D Programming Language |url=https://dlang.org/spec/attribute.html |website=dlang.org |access-date=2018-06-22 |archive-date=2018-12-08 |archive-url=https://web.archive.org/web/20181208115642/https://dlang.org/spec/attribute.html |url-status=live }}</ref>
* In [[DIGITAL Command Language]], the @ character was the command used to execute a command procedure. To run the command procedure VMSINSTAL.COM, one would type <code>@VMSINSTAL</code> at the command prompt.
* In the [[Domain Name System]] (DNS), @ is used to represent the {{code|$ORIGIN}}, typically the "root" of the domain without a prefixed sub-domain. (Ex: wikipedia.org vs. www.wikipedia.org)
* In [[Forth (programming language)|Forth]], it is used to fetch values from the address on the top of the stack. The operator is pronounced as "fetch".
* In [[Haskell]], it is used in so-called ''as-patterns''. This notation can be used to give aliases to [[pattern matching|patterns]], making them more readable.
* in [[HTML]], it can be encoded as <code>&amp;commat;</code><ref>{{cite web |url=https://dev.w3.org/html5/html-author/charref |title=Character Entity Reference Chart |date= |website=[[World Wide Web Consortium]] (W3C) |access-date=2022-02-08 |archive-date=2021-02-27 |archive-url=https://web.archive.org/web/20210227130216/https://dev.w3.org/html5/html-author/charref |url-status=live }}</ref>
* In [[J (programming language)|J]], denotes [[function composition]].
* In [[Java (programming language)|Java]], it has been used to denote [[Java annotation|annotations]], a kind of metadata, since version 5.0.<ref>{{Cite web |title=in java what does the @ symbol mean? |url=https://stackoverflow.com/questions/31822020/in-java-what-does-the-symbol-mean |access-date=2020-04-30 |website=Stack Overflow |archive-date=2020-07-26 |archive-url=https://web.archive.org/web/20200726125845/https://stackoverflow.com/questions/31822020/in-java-what-does-the-symbol-mean |url-status=live }}</ref>
* In [[Julia (programming language)|Julia]], it denotes the invocation of a macro.<ref>{{cite web |title=Metaprogramming · The Julia Language |url=https://docs.julialang.org/en/v1/manual/metaprogramming/#man-macros |website=docs.julialang.org |access-date=2023-08-23 |archive-date=2023-06-23 |archive-url=https://web.archive.org/web/20230623204719/https://docs.julialang.org/en/v1/manual/metaprogramming/ |url-status=live }}</ref>
* In [[LiveCode]], it is prefixed to a parameter to indicate that the parameter is [[Pass by reference|passed by reference]].
* In an [[LXDE]] autostart file (as used, for example, on the [[Raspberry Pi]] computer), @ is prefixed to a command to indicate that the command should be automatically re-executed if it crashes.<ref>{{Cite web |title=LXSession - LXDE.org |url=https://wiki.lxde.org/en/LXSession#Settings |access-date=2020-04-30 |website=wiki.lxde.org |archive-date=2020-07-14 |archive-url=https://web.archive.org/web/20200714075921/https://wiki.lxde.org/en/LXSession#Settings |url-status=live }}</ref>
* In a [[Makefile]], @ specifies to not output the command before it is executed.
* In [[ML (programming language)|ML]], it denotes list concatenation.
* In [[modal logic]], specifically when representing [[possible world]]s, @ is sometimes used as a logical symbol to denote the actual world (the world we are "at").
* In [[Objective-C]], @ is prefixed to language-specific keywords such as @implementation and to form string literals.
* In InterSystems [[Caché ObjectScript|ObjectScript]], @ is the indirection operator, enabling dynamic runtime substitution of part or all of a command line, a command, or a command argument.<ref>{{Cite web |title=Indirection – InterSystems IRIS Documentation|url=https://docs.intersystems.com/irislatest/csp/docbook/DocBook.UI.Page.cls?KEY=RCOS_op_indirection|access-date=2025-01-31|website=docs.intersystems.com|language=en-us|url-status=live}}</ref>
* In [[Pascal (programming language)|Pascal]], @ is the "address of" operator (it tells the location at which a variable is found).
* In [[Perl]], @ prefixes [[Variable (programming)|variables]] which contain [[Array data structure|arrays]] {{code|@array}}, including array [[Array slicing#1987: Perl|slices]] {{code|@array[2..5,7,9]}} and [[Hash table#Associative arrays|hash]] slices {{code|@hash{'foo', 'bar', 'baz'}|perl}} or {{code|@hash{qw(foo bar baz)}|perl}}. This use is known as a ''[[Sigil (computer programming)|sigil]]''.
* In [[PHP]], it is used just before an [[Expression (programming)|expression]] to make the [[Interpreter (computing)|interpreter]] suppress errors that would be generated from that expression.<ref>{{Cite web |title=PHP: Error Control Operators – Manual |url=https://www.php.net/manual/en/language.operators.errorcontrol.php |access-date=2020-04-30 |website=www.php.net |archive-date=2020-05-08 |archive-url=https://web.archive.org/web/20200508094533/https://www.php.net/manual/en/language.operators.errorcontrol.php |url-status=live }}</ref>
* In [[Python (programming language)|Python]] 2.4 and up, it is used to [[Python syntax and semantics#Decorators|decorate a function]] (wrap the function in another one at creation time). In Python 3.5 and up, it is also used as an [[Overload (programming)|overloadable]] [[matrix multiplication]] operator.<ref>{{Cite web |title=syntax – What does the "at" (@) symbol do in Python? |url=https://stackoverflow.com/questions/6392739/what-does-the-at-symbol-do-in-python |access-date=2020-04-30 |website=Stack Overflow |archive-date=2020-04-24 |archive-url=https://web.archive.org/web/20200424180918/https://stackoverflow.com/questions/6392739/what-does-the-at-symbol-do-in-python |url-status=live }}</ref>
*In [[R (programming language)|R]] and [[S-PLUS]], it is used to extract slots from S4 objects.<ref>{{Cite web |title= The S4 object system |url=http://adv-r.had.co.nz/S4.html |access-date=2023-08-18 |website=adv-r.had.co.nz/ |archive-date=2022-12-06 |archive-url=https://web.archive.org/web/20221206085835/http://adv-r.had.co.nz/S4.html |url-status=live }}</ref>
*In [[ASP.NET Razor|Razor]], it is used for [[C Sharp (programming language)|C#]] code blocks.<ref>{{Cite web |title=Usage of the @ (at) sign in ASP.NET |url=https://www.mikesdotnetting.com/article/258/usage-of-the-at-sign-in-asp-net |access-date=2020-04-30 |website=www.mikesdotnetting.com |archive-date=2020-04-04 |archive-url=https://web.archive.org/web/20200404105645/http://www.mikesdotnetting.com/article/258/usage-of-the-at-sign-in-asp-net |url-status=live }}</ref>
* In [[Ruby (programming language)|Ruby]], it functions as a sigil: <code>@</code> prefixes [[instance variable]]s, and <code>@@</code> prefixes [[class variable]]s.<ref>{{Cite web |title=syntax – What does @@variable mean in Ruby? |url=https://stackoverflow.com/questions/5890118/what-does-variable-mean-in-ruby |access-date=2020-05-05 |website=Stack Overflow |archive-date=2020-07-26 |archive-url=https://web.archive.org/web/20200726105629/https://stackoverflow.com/questions/5890118/what-does-variable-mean-in-ruby |url-status=live }}</ref>
* In [[Rust (programming language)|Rust]], it is used to bind values matched by a pattern to a variable.<ref>{{cite web |title=Patterns |url=https://doc.rust-lang.org/reference/patterns.html#identifier-patterns |website=The Rust Reference |access-date=21 July 2023 |archive-url=https://web.archive.org/web/20230618030139/https://doc.rust-lang.org/reference/patterns.html#identifier-patterns |archive-date=18 June 2023 |url-status=live}}</ref>
* In [[Scala (programming language)|Scala]], it is used to denote annotations (as in Java), and also to bind names to subpatterns in pattern-matching expressions.<ref>{{Cite web |title=Scala @ operator |url=https://stackoverflow.com/questions/2359014/scala-operator |access-date=2020-05-05 |website=Stack Overflow |archive-date=2020-07-26 |archive-url=https://web.archive.org/web/20200726112338/https://stackoverflow.com/questions/2359014/scala-operator |url-status=live }}</ref>
* In [[Swift (programming language)|Swift]], <code>@</code> prefixes "annotations" that can be applied to classes or members. Annotations tell the compiler to apply special semantics to the declaration like keywords, without adding keywords to the language.
* In [[T-SQL]], <code>@</code> prefixes variables and <code>@@</code> prefixes "niladic" system functions.
* In several [[xBase]]-type programming languages, like [[DBASE]], [[FoxPro]]/[[Visual FoxPro]] and [[Clipper (programming language)|Clipper]], it is used to denote position on the screen. For example: {{code|@1,1 SAY "HELLO"|xbase}} to show the word "HELLO" in line 1, column 1.
** In FoxPro/Visual FoxPro, it is also used to indicate explicit [[pass by reference]] of variables when calling [[Subroutine|procedures or functions]] (but it is not an [[Memory address|address]] [[Operator (programming)|operator]]).<ref>{{Cite web |title=Visual FoxPro Programming Language Online Help: SET UDFPARMS (Command), or MSDN Library 'How to: Pass Data to Parameters by Reference'. |date=18 June 2008 |url=http://msdn.microsoft.com/en-us/library/z9b11381.aspx |access-date=2011-02-19 |publisher=Microsoft, Inc. |archive-date=2012-10-22 |archive-url=https://web.archive.org/web/20121022193155/http://msdn.microsoft.com/en-us/library/z9b11381.aspx |url-status=live }}</ref>
* In a Windows [[Batch file]], an <code>@</code> at the start of a line suppresses the [[Echo (command)|echoing]] of that command. In other words, is the same as <code>ECHO OFF</code> applied to the current line only. Normally a Windows command is executed and takes effect from the next line onward, but <code>@</code> is a rare example of a command that takes effect immediately. It is most commonly used in the form {{code|@echo off}} which not only switches off echoing but prevents the command line itself from being echoed.<ref>{{Cite web |title=echo |url=https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/echo |website=docs.microsoft.com |access-date=2018-09-11 |archive-date=2018-09-11 |archive-url=https://web.archive.org/web/20180911191929/https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/echo |url-status=live }}</ref><ref>{{Cite web |title=Echo - Windows CMD - SS64.com |url=https://ss64.com/nt/echo.html |website=ss64.com |access-date=2018-09-11 |archive-date=2018-09-11 |archive-url=https://web.archive.org/web/20180911191818/https://ss64.com/nt/echo.html |url-status=live }}</ref>
* In [[Windows PowerShell]], @ is used as array operator for array and hash table literals and for enclosing here-string literals.<ref>{{Cite web |title=Windows PowerShell Language Specification Version 3.0 |url=http://www.microsoft.com/en-us/download/details.aspx?id=36389 |website=Microsoft Download Center |access-date=2013-10-29 |archive-date=2022-01-26 |archive-url=https://web.archive.org/web/20220126032007/https://www.microsoft.com/en-us/download/details.aspx?id=36389 |url-status=live }}</ref>

=== Gender neutrality in Spanish ===
[[File:Madrid - Acampada Sol - 110521 192211.jpg|right|upright|thumb|Protester with banner showing "La revolución está en nosotr@s"]]
{{Main|Gender neutrality in Spanish}}
In [[Spanish language|Spanish]], where many words end in "-o" when in the masculine [[Grammatical gender|gender]] and end "-a" in the feminine, @ is sometimes used as a [[gender-neutral pronoun|gender-neutral]] substitute for the default "o" ending.<ref>{{Cite journal |last=Martell-Otero |first=Loida |date=Fall 2009 |title=Doctoral Studies as Llamamiento, or How We All Need to be 'Ugly Betty' |journal=Perspectivas |pages=84–106}}</ref> For example, the word ''amigos'' traditionally represents not only male friends, but also a mixed group, or where the genders are not known. The proponents of gender-inclusive language would replace it with ''amig@s'' in these latter two cases, and use ''amigos'' only when the group referred to is all-male and ''amigas'' only when the group is all female. The [[Real Academia Española]] disapproves of this usage.<ref>{{Cite web |title=Diccionario panhispánico de dudas |url=https://www.rae.es/dpd/ |website=«Diccionario panhispánico de dudas» |access-date=2021-04-02 |archive-date=2021-04-06 |archive-url=https://web.archive.org/web/20210406113617/https://www.rae.es/dpd/ |url-status=live }}</ref>

=== 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.