unconventional vs alternative

unconventional is not a noun while alternative is a noun.

Word	Noun	Adjective	Verb	Adverb
unconventional	No	Yes	No	No
alternative	Yes	Yes	No	No

unconventional (noun)	alternative (noun)
	one of a number of things from which only one can be chosen

unconventional (adjective)	alternative (adjective)
not conforming to accepted rules or standards	necessitating a choice between mutually exclusive possibilities
not conventional or conformist	serving or used in place of another
not conforming to legality, moral law, or social convention	pertaining to unconventional choices