functional vs role

functional is not a noun while role is a noun.

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

functional (noun)	role (noun)
	the actions and activities assigned to or required or expected of a person or group
	normal or customary activity of a person in a particular social setting
	what something is used for
	an actor's portrayal of someone in a play

functional (adjective)	role (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