unidentified vs unknown

unidentified is not a noun while unknown is a noun.

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

As adjectives, unidentified and unknown are synonyms defined as:

Other synonyms of unidentified include nameless, unnamed.

unidentified (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

unidentified (adjective)	unknown (adjective)
being or having an unknown or unnamed source	not known
not yet identified	being or having an unknown or unnamed source
	not famous or acclaimed
	not known before
	not known to exist