unbelieving vs agnostic

unbelieving is not a noun while agnostic is a noun.

Word	Noun	Adjective	Verb	Adverb
unbelieving	No	Yes	No	No
agnostic	Yes	Yes	No	No

unbelieving (noun)	agnostic (noun)
	a person who claims that they cannot have true knowledge about the existence of God (but does not deny that God might exist)
	someone who is doubtful or noncommittal about something

unbelieving (adjective)	agnostic (adjective)
holding that only material phenomena can be known and knowledge of spiritual matters or ultimate causes is impossible	uncertain of all claims to knowledge
denying or questioning the tenets of especially a religion	of or pertaining to an agnostic or agnosticism
rejecting any belief in gods