biology vs mental

biology is a noun but mental is not a noun.

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

biology (noun)	mental (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

biology (adjective)	mental (adjective)
	involving the mind or an intellectual process
	of or relating to the mind
	of or relating to the chin- or liplike structure in insects and certain mollusks
	of or relating to the chin or median part of the lower jaw
	affected by a disorder of the mind