For the article on , the Irish writer, see: George William Russell

" ", or " ", is a vowel and a grapheme used in the Icelandic, Danish, Faroese and Norwegian alphabets. It was also used in Old English and in medi val and early modern Latin. Modern English still contains several words that use , such as Encyclop dia, but it is falling into disuse. The origin of the letter is a ligature for AE.

In Icelandic, the letter signifies a diphthong (IPA [ai]). The same goes in Faroese for the so-called long (IPA [ɛa]), whereas the short is a simple [a]. In Danish and Norwegian, represents a simple vowel, namely IPA [ɛ] and [ ], respectively. The same phoneme is represented in Swedish by the letter "German by "A-Umlaut" (written ).

In Old English, the ligature was used to denote a sound intermediate between those of "A" and "E" (IPA [ ]), very much like the short "A" of cat in many dialects of modern English. In this context, the name of the letter is sc (Ash in modern English, meaning the tree), after the name of the corresponding rune ᚫ in the Anglo-Saxon Futhorc related to the Older Futhark As rune.

In Classical Latin, the combination denotes a diphthong (IPA [ae̯]) that had a value similar to the long "I" in most dialects of modern English. It was used both in native words (spelled with "AI" before the 2nd century BC) and in borrowings from Greek words having the diphthong "AI" ("ΑΙ"). Both classical and modern practice is to write the letters separately, but the ligature was used in medieval and early modern writings, in part because " " was reduced to a simple long vowel (IPA [e:]) in late Latin.

The symbol [ ] is also used in the International Phonetic Alphabet to denote the sound of the Old English letter, a near-open front unrounded vowel, as in the modern English word cat. In this context, it is always lowercase.

For computers, when using the Latin-1 or Unicode sets, the codes for ' ' and ' ' are respectively 0198 and 0230 (holding down the ALT key whilst typing in 0198 on the number pad will produce the character on Windows systems and holding down the option or alt key (⌥) whilst typing an apostrophe (') on a United States Macintosh keyboard), or C6 and E6 in hexadecimal. In HTML, the HTML character entity references Æ and æ have been assigned to and , respectively.

The progressive metal band Tool used an for the title of their third album, nima, and the song nema off of that album. This is similar to the usage of the heavy metal umlaut, but is meant as a combination of anima and enema.