digraph in certain Greek or Latin words; it developed in later Latin where classical Latin used separate letters. The Latin digraph also was used to transliterate Greek -ai- (as in aegis). When Latinate words flooded English in the 16c. it came with them, but as an etymological device only, and it was pronounced simply "e" and eventually reduced to that letter in writing (as in eon, Egypt) in most cases, excepting (until recently) proper names (Cæsar, Æneas, Æsculapius, Æsop). When divided and representing two syllables (aerate, aerial) it sometimes is written aë.
Anglo-Saxon alphabetic character representing a simple vowel corresponding to the short "a" in glad or the long one in dare, ultimately from Latin and used by scribes writing Old English because it represented roughly the same sound as Latin æ (see æ (1)). In Middle English the vowel tended to become -a- when short (glad, sad, from Old English glæd, sæd, etc.), -e- when long.