Main Entry: ae·on

Variant(s): or eon \ˈē-ən, ˈē-ˌän\

Function: noun

Etymology: Latin, from Greek aiōn — more at aye

Date: 1647

1 : an immeasurably or indefinitely long period of time : age
2 a usually eon : a very large division of geologic time usually longer than an era b : a unit of geologic time equal to one billion years