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 say the rings offer a unique opportunity to dissect the complex interplay of stellar outflow over eons. —Sharmila Kuthunur, Space.com, 15 Apr. 2025

In some ways, 2000 seemed like yesterday ... and eons ago. —Joanna Allhands, The Arizona Republic, 31 Dec. 2024

While different religions and ancient cultures had described the planet as animate for eons, Lovelock’s contemporaries in the scientific community were more apt to shun this notion, preferring a Darwinian stance that species adapted to their environments, but not vice versa. —Joe Spring, Smithsonian Magazine, 9 Dec. 2024

From the Asian elephant to the gharial, there’s a staggering array of native wildlife that’s been calling India home for eons, with no shortage of iconic mammals, birds and reptiles to be found during a visit. —Jared Ranahan, Forbes.com, 3 Apr. 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