eon · aeon
an immeasurable age
Today this word meansTime beyond reckoning. In geology, the largest division of geologic time.
Greek aiōn meant a lifetime, and by extension time stretching on without end.
The word raised into a god, Aion, is a god who sees time as a circle — the counterpart to Chronos, time that flows.
In geology it names spans of hundreds of millions of years — the Phanerozoic, the Proterozoic.