Æ
"Æ", "æ" is a vowel and a letter used in the Icelandic, Danish and Norwegian alphabets. It was also used in Old English, and in medieval and early modern Latin.
The origin of the letter is a ligature for "ae" that has become a letter in itself. But in modern Danish, Icelandic and Norwegian, the letter is a unique vowel in itself, not a diphthong, umlaut or ligature. In German and Swedish, the letter "Ä" ("A" with a diaeresis) is the equivalent.
In Latin, the ligature is used to denote derivations from the Greek diphthong "ai" ("αι"). The Latin practice currently favored by classical editors, however, is to write the letters separately.
For computers, when using the Latin-1 or Unicode sets, the codes for 'Æ' and 'æ' are respectively 198 and 230, or C6 and E6 in hexadecimal. In HTML, you can also use the HTML character entity references Æand æ.