exact vs exactness

exact is not a noun while exactness is a noun.

Word	Noun	Adjective	Verb	Adverb
exact	No	Yes	Yes	No
exactness	Yes	No	No	No

exact (noun)	exactness (noun)
	the quality of being exact

exact (adjective)	exactness (adjective)
marked by strict and particular and complete accordance with fact
(of ideas, images, representations, expressions) characterized by perfect conformity to fact or truth; strictly correct
lacking compromising or mitigating elements

exact (verb)	exactness (verb)
claim as due or just
take as an undesirable consequence of some event or state of affairs