unknown vs anon.

unknown is a noun but anon. is not a noun.

Word	Noun	Adjective	Verb	Adverb
unknown	Yes	Yes	No	No
anon.	No	Yes	No	No

unknown (noun)	anon. (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)	anon. (adjective)
not known	having no known name or identity or known source
being or having an unknown or unnamed source
not famous or acclaimed
not known before
not known to exist