aquifer vs geological formation

aquifer and geological formation both are nouns.

Word	Noun	Adjective	Verb	Adverb
aquifer	Yes	No	No	No
geological formation	Yes	No	No	No

As nouns, geological formation is a hypernym of aquifer; that is, geological formation is a word with a broader meaning than aquifer:

aquifer: underground bed or layer yielding ground water for wells and springs etc
geological formation: (geology) the geological features of the earth

Other hypernyms of aquifer include formation.

aquifer (noun)	geological formation (noun)
underground bed or layer yielding ground water for wells and springs etc	(geology) the geological features of the earth