unfamiliar vs unknown

unfamiliar is not a noun while unknown is a noun.

Word	Noun	Adjective	Verb	Adverb
unfamiliar	No	Yes	No	No
unknown	Yes	Yes	No	No

unfamiliar (noun)	unknown (noun)
	a variable whose values are solutions of an equation
	an unknown and unexplored region
	anyone who does not belong in the environment in which they are found

unfamiliar (adjective)	unknown (adjective)
not known or well known	not known
	being or having an unknown or unnamed source
	not famous or acclaimed
	not known before
	not known to exist