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

Oil itself may take eons to create, but the industry never stops. — Brian Sullivan, CNBC, 1 Oct. 2026

Fathoms below and eons ago Hydrothermal systems created by other impacts are all over the planet. — Elizabeth Rayne, ArsTechnica, 30 Sep. 2026

Tom Cruise has dangled from cliffs, skyscrapers and planes, but oil magnate Digger Rockwell is his riskiest role in eons. — Amy Nicholson, Los Angeles Times, 29 Sep. 2026

Now researchers analyzing data from those collisions have seen an unexpected signal that offers new clues about how the cosmic transition happened eons ago. — Clara Moskowitz, Scientific American, 28 Sep. 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
• european
• grammarian
• hercynian
• huronian
• jacobean
• maccabean
• manichaean
• manichean
• mullerian

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