facultative vs biology

facultative is not a noun while biology is a noun.

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

facultative (noun)	biology (noun)
	the science that studies living organisms
	all the plant and animal life of a particular region
	characteristic life processes and phenomena of living organisms

facultative (adjective)	biology (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