a challenge!

æ has come and gone throughout the development of English... mostly gone. it disappeared almost entirely by C13 and was reintroduced in C16 in words derived from Latin and Greek; but this had only etymological value, and when the word became thorougly English, the ae became simply e.

æ or ae now remains only (1) in Greek and Lat. proper names as in Æneas, Cæsar; even these, when familiar, often take e as Judea, Etna; (2) in words belonging to Roman or Gr. Antiquities as ædile, ægis; (3) in scientific or technical terms as ætiology, æstivation, phænogamous, Athenæum; these also when they become popularized take e, as phenomenon, Lyceum, museum, era.

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