functioning vs functional

functioning is a noun but functional is not a noun.

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

functioning (noun)	functional (noun)
process or manner of functioning or operating

functioning (adjective)	functional (adjective)
performing or able to perform its regular function	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