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

People have marked solstices for eons with festivals and monuments, including Sweden's midsummer eve celebrations and Stonehenge, which was designed to align with the sun’s paths at the solstices. —ABC News, 19 June 2026

Over eons of mythmaking, the 13th century bandit Robin Hood has evolved from a scamp adored by King Henry VIII to a symbol of sticking it to the rich. —Amy Nicholson, Los Angeles Times, 18 June 2026

Or, instead all its fragments may have scattered into the asteroid belt to rain down as angrites across the eons, says William Bottke, a solar system scientist at the Southwest Research Institute, who was uninvolved with the study. —Jenna Ahart, Scientific American, 9 June 2026

People have been doing it for eons. —Baz Bamigboye, Deadline, 2 June 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