atsign

The at sign, or at symbol, is a typographic character used to denote "at" in various contexts. It is widely recognized as the separator in email addresses between the user name and the domain and is used on social media to indicate mentions or tags, as in example usernames prefixed with @. The symbol is encoded in ASCII as 64 and in Unicode as U+0040.

Etymology and early history: The character originated as a ligature of the letters a and t and was used by merchants in medieval and early modern Europe to indicate "at" in prices, such as "3 items @ 5d" to denote price per unit. The symbol appeared in early printing and bookkeeping, but its use outside specialized commerce diminished over time.

Modern development: Ray Tomlinson selected the "@" for email addressing in 1971 on the ARPANET project because it was a distinctive character not commonly used in names and would not cause conflicts across systems. Since then, it has become universal in email addresses. In the 2000s the symbol gained a new role on social media as a prefix to user handles to mention or link to accounts; this convention has been adopted by many platforms, with minor variations.

Internationalization and names: Many languages have their own names for the symbol. Examples include arobase in French, arroba in Spanish and Portuguese, chiocciola in Italian, and apenstaartje or at-teken in Dutch, with Klammeraffe (monkey composer) among German speakers. The character remains a common input on keyboards and a standard punctuation mark in programming languages and data formats.