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

Examples of eon in a Sentence

Recent Examples on the Web

According to one popular hypothesis, the pot had eventually boiled over: after eons of frustrated heating, some 800 million years ago, the planet’s outer shell buckled, and Venus’s entire surface was paved over with immense outpourings of fresh lava. —Elise Cutts, Scientific American, 13 May 2025

All over the world, wild plants like these—vital members of ecosystems and unique products of eons of evolution—are losing ground. —Katarina Zimmer, Smithsonian Magazine, 2 May 2025

The secret lies in a remarkable genetic and biochemical toolkit honed through eons of evolutionary pressure. —Scott Travers, Forbes, 24 Mar. 2025

These stellar exiles can travel across space for eons before ending up infiltrating unrelated nebulas like Sh2-46, according to the statement. —Sharmila Kuthunur, Space.com, 9 May 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