faculty vs facultative

faculty is a noun but facultative is not a noun.

Word	Noun	Adjective	Verb	Adverb
faculty	Yes	No	No	No
facultative	No	Yes	No	No

faculty (noun)	facultative (noun)
one of the inherent cognitive or perceptual powers of the mind
the body of teachers and administrators at a school

faculty (adjective)	facultative (adjective)
	able to exist under more than one set of conditions
	of or relating to the mental faculties
	granting a privilege or permission or power to do or not do something
	optional