That little a with a circle curling around it that is found in email addresses is most commonly referred to as the at symbol.
　　小寫字母a外加個圓圈，這一符號常出現在email（電子郵件）地址中，通常是作為at(在)的標記。

　　Surprisingly though, there is no official, universal name for this sign. There are dozens of strange terms to describe the @ symbol.
　　然而令人感到驚奇的是，這一標記居然沒有官方的，通用的名稱。有幾十個奇怪的術語用來描繪@這一符號。

　　Before it became the standard symbol for electronic mail, the @ symbol was used to represent the cost or weight of something. For instance, if you purchased 6 apples, you might write it as 6 apples @ $1.10 each.
　　@這一符號在成為電子郵件的標準符號之前，曾被用來表示物品的單價或質量。例如，你買6只蘋果。就可以寫成六只蘋果，每只@$1.10，表示每只蘋果1.10美元。

　　With the introduction of e-mail came the popularity of the @ symbol. The @ symbol or the at sign separates a person’s online user name from his mail server address. For instance, joe@uselessknowledge.com. Its widespread use on the Internet made it necessary to put this symbol on keyboards in other countries that have never seen or used the symbol before. As a result, there is really no official name for this symbol.
　　隨著電子郵件的使用，@這一符號越來越普及了。符號@或’at’標記將上網用戶的姓名與其郵件的服務器地址分開。例如：joe@uselessknowledge.com。 這一符號在因特網上的廣泛使用使得許多以前從未見過或使用過它的國家必須在它們的電腦鍵盤上加上這一符號鍵，結果造成這一符號并沒有真正的官方名稱。

　　The actual origin of the @ symbol remains an enigma.
　　@符號的確切起源仍然是謎。

　　History tells us that the @ symbol stemmed from the tired hands of the medieval monks. During the Middle Ages before the invention of printing presses, every letter of a word had to be painstakingly transcribed by hand for each copy of a published book. The monks that performed these long, tedious copying duties looked for ways to reduce the number of individual strokes per word for common words. Although the word at is quite short to begin with, it was a common enough word in texts and documents that medieval monks thought it would be quicker and easier to shorten the word at even more. As a result, the monks looped the t around the a and created it into a circle-eliminating two strokes of the pen.
　　歷史告訴我們，@這一符號起源于中世紀僧侶疲勞的雙手。中世紀時印刷機尚未發明，要出版一本書，每一個單詞的每一個字母都得用手工辛苦的刻出來。從事這項長時間辛苦謄寫刻畫的僧侶們就開始尋找減少每一個常用字筆畫數的方法。雖然at這一單詞開始寫起來很短，但它在文本和文件中頻繁出現。中世紀的僧侶們就想到如果能進一步簡化它，就可以寫起來更快更容易。結果，僧侶們就在a四周畫了一個圈，從而省卻了字母t的兩個筆劃。