Precambrian vs Precambrian aeon

Precambrian and Precambrian aeon both are nouns.

Word	Noun	Adjective	Verb	Adverb
Precambrian	Yes	No	No	No
Precambrian aeon	Yes	No	No	No

As nouns, Precambrian and Precambrian aeon are synonyms defined as:

Precambrian and Precambrian aeon: the eon following the Hadean time and preceding the Phanerozoic eon; from about 3,800 million years ago until 544 million years ago

Other synonyms of Precambrian include Precambrian eon, Precambrian period.

Precambrian (noun)	Precambrian aeon (noun)
the eon following the Hadean time and preceding the Phanerozoic eon; from about 3,800 million years ago until 544 million years ago	the eon following the Hadean time and preceding the Phanerozoic eon; from about 3,800 million years ago until 544 million years ago