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

• forever
• months
• long
• age

Examples of eon in a Sentence

Recent Examples on the Web

What epic tales might try to picture the explosion of the supervolcano in the Rocky Mountains and the gigantic crater lake of bubbling acid that eons ago swallowed places called Montana, Idaho, and Wyoming? —Literary Hub, 22 Oct. 2025

That would be the mythical city lost to the sea eons ago. —Ashley Miznazi, Miami Herald, 21 Oct. 2025

Over the eons, this activity has regularly caused major earthquakes. —Jack Tamisiea, Scientific American, 10 Oct. 2025

Harnessing these forensic investigations, the team leverages the latest science to reveal superpower adaptations and migration patterns that have been taking place for eons. —Jesse Whittock, Deadline, 9 Oct. 2025

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