aeon

UK: /ˈiːɒn/ US: /ˈiən, ˈiɑn/ ,(ē′ən, ē′on)

WordReference Random House Learner's Dictionary of American English © 2026

ae•on /ˈiən, ˈiɑn/   n. 

1. eon.

WordReference Random House Unabridged Dictionary of American English © 2026

ae•on  (ē′ən, ē′on), n. 

1. (in Gnosticism) one of a class of powers or beings conceived as emanating from the Supreme Being and performing various functions in the operations of the universe.
2. eon.

• Greek aió̄n space of time, age
• Late Latin
• 1640–50

Collins Concise English Dictionary © HarperCollins Publishers::

aeon, eon / ˈiːən ˈiːɒn/ noun

1. an immeasurably long period of time; age
2. a period of one thousand million years

Etymology: 17th Century: from Greek aiōn an infinitely long time

WordReference Random House Learner's Dictionary of American English © 2026

e•on /ˈiən, ˈiɑn/   n. [countable]

1. a very long period of time.

WordReference Random House Unabridged Dictionary of American English © 2026

e•on  (ē′ən, ē′on), n. 

1. an indefinitely long period of time;
   age.
2. Geology the largest division of geologic time, comprising two or more eras.
3. Astronomy one billion years.

Also, aeon. 

• see aeon

Collins Concise English Dictionary © HarperCollins Publishers::

eon / ˈiːən ˈiːɒn/ noun

1. the usual US spelling of aeon