eon

noun

ˈē-ən  ˈē-ˌän 

variants or chiefly British aeon

1

: an immeasurably or indefinitely long period of time : age

I haven't seen him in eons.

2

a

: a very large division of geologic time usually longer than an era

the Archean eon

b

: a unit of geologic time equal to one billion years

Synonyms of eon

• forever
• months
• long
• age

Examples of eon in a Sentence

Recent Examples on the Web

Unlike rocks on Earth, which have been exposed to eons of weather and geological processes, many meteorites have spent that time hurtling through space, relatively untouched, Fries said. —Maliya Ellis, Houston Chronicle, 5 Apr. 2026

Telescopes and microscopes were everywhere by then, shrinking and stretching the Earth and sky and, in the process, expanding archaeological time from centuries to eons. —Kathryn Hughes, The New York Review of Books, 4 Apr. 2026

But Villaraigosa left City Hall in 2013 — eons ago in the world of politics. —Los Angeles Times, 16 Mar. 2026

But that was more than five years ago — eons in American politics. —Frank Langfitt, NPR, 12 Mar. 2026

Word History

Etymology

borrowed from Late Latin aeōn "age (in the world's history), evil spirit (in Gnosticism)," borrowed from Greek aiṓn "lifetime, long period of time, age" — more at aye entry 3

First Known Use

circa 1642, in the meaning defined at sense 1

Rhymes for eon

• adlerian
• caesarian
• cyclopean
• empyrean
• euclidean
• european
• grammarian
• hercynian
• huronian
• jacobean
• kampuchean
• maccabean

Kids Definition

eon

noun

ˈē-ən

1

: a very long period of time

2

a

: a very large division of geologic time usually longer than an era

b

: a unit of geologic time equal to one billion years