abstruse vs abstruseness

abstruse is not a noun while abstruseness is a noun.

Word	Noun	Adjective	Verb	Adverb
abstruse	No	Yes	No	No
abstruseness	Yes	No	No	No

abstruse (noun)	abstruseness (noun)
	the quality of being unclear or abstruse and hard to understand
	wisdom that is recondite and abstruse and profound

abstruse (adjective)	abstruseness (adjective)
difficult to penetrate; incomprehensible to one of ordinary understanding or knowledge