optional vs facultative

optional and facultative both are adjectives.

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

optional (adjective)	facultative (adjective)
possible but not necessary; left to personal choice	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