mental faculty vs ability

mental faculty and ability both are nouns.

Word	Noun	Adjective	Verb	Adverb
mental faculty	Yes	No	No	No
ability	Yes	No	No	No

As nouns, ability is a hypernym of mental faculty; that is, ability is a word with a broader meaning than mental faculty:

mental faculty: one of the inherent cognitive or perceptual powers of the mind
ability: possession of the qualities (especially mental qualities) required to do something or get something done

Other hypernyms of mental faculty include power.

mental faculty (noun)	ability (noun)
one of the inherent cognitive or perceptual powers of the mind	the quality of being able to perform; a quality that permits or facilitates achievement or accomplishment
	possession of the qualities (especially mental qualities) required to do something or get something done