Phanerozoic aeon vs Phanerozoic eon

Phanerozoic aeon and Phanerozoic eon both are nouns.

Word	Noun	Adjective	Verb	Adverb
Phanerozoic aeon	Yes	No	No	No
Phanerozoic eon	Yes	No	No	No

As nouns, Phanerozoic aeon and Phanerozoic eon are synonyms defined as:

Phanerozoic aeon and Phanerozoic eon: the period from about 540 million years ago until the present, a period when abundant life existed

Other synonyms of Phanerozoic aeon include Phanerozoic.

Phanerozoic aeon (noun)	Phanerozoic eon (noun)
the period from about 540 million years ago until the present, a period when abundant life existed	the period from about 540 million years ago until the present, a period when abundant life existed