retentiveness vs mental faculty

retentiveness and mental faculty both are nouns.

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

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

retentiveness: the power of retaining and recalling past experience
mental faculty: one of the inherent cognitive or perceptual powers of the mind

Other hypernyms of retentiveness include faculty, module.

retentiveness (noun)	mental faculty (noun)
the property of retaining possessions that have been acquired	one of the inherent cognitive or perceptual powers of the mind
the power of retaining liquid
the power of retaining and recalling past experience