unknown vs strange

unknown is a noun but strange is not a noun.

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

As adjectives, unknown and strange are synonyms defined as:

unknown (noun)	strange (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

unknown (adjective)	strange (adjective)
not known	being definitely out of the ordinary and unexpected; slightly odd or even a bit weird
being or having an unknown or unnamed source	relating to or originating in or characteristic of another place or part of the world
not famous or acclaimed	not known before
not known before
not known to exist