contentiousness vs contentious

contentiousness is a noun but contentious is not a noun.

Word	Noun	Adjective	Verb	Adverb
contentiousness	Yes	No	No	No
contentious	No	Yes	No	No

contentiousness (noun)	contentious (noun)
an inclination to be quarrelsome and contentious

contentiousness (adjective)	contentious (adjective)
	inclined or showing an inclination to dispute or disagree, even to engage in law suits
	involving or likely to cause controversy