pathology vs functional

pathology is a noun but functional is not a noun.

Word	Noun	Adjective	Verb	Adverb
pathology	Yes	No	No	No
functional	No	Yes	No	No

pathology (noun)	functional (noun)
the branch of medical science that studies the causes and nature and effects of diseases
any deviation from a healthy or normal condition

pathology (adjective)	functional (adjective)
	designed for or capable of a particular function or use
	involving or affecting function rather than physiology
	relating to or based on function especially as opposed to structure
	(of e.g. a machine) performing or capable of performing
	designed for or adapted to a function or use
	fit or ready for use or service