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

Scientists suspect the Neretva Vallis channel was carved out eons ago, by water gushing into the crater. —Sharmila Kuthunur, Space.com, 14 Mar. 2025

But while sometimes gaming is immune to inflation (like the $60 game price point that lasted eons and only just moved up to $70), there are also other issues to consider like the current Switch chip costing $80 a unit, while the new one, an analyst estimates, may be $130-$150 instead. —Paul Tassi, Forbes, 14 Mar. 2025

Inside, the craggy walls of the massive chamber are a rainbow of reds, oranges, yellows and greens, thanks to eons of mineral deposits. —Emily Matchar, Smithsonian Magazine, 27 Jan. 2025

In contrast to the regional and historical topics of the first two editions, science and technology are by definition rapidly evolving, and five years can represent an eon of development and change. —Bryan Barcena, Artforum, 1 Jan. 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