decisive vs decisiveness

decisive is not a noun while decisiveness is a noun.

Word	Noun	Adjective	Verb	Adverb
decisive	No	Yes	No	No
decisiveness	Yes	No	No	No

decisive (noun)	decisiveness (noun)
	the trait of resoluteness as evidenced by firmness of character or purpose
	the quality of being final or definitely settled

decisive (adjective)	decisiveness (adjective)
determining or having the power to determine an outcome
characterized by decision and firmness
forming or having the nature of a turning point or crisis
unmistakable