contention vs contentious

contention is a noun but contentious is not a noun.

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

contention (noun)	contentious (noun)
the act of competing as for profit or a prize
a contentious speech act; a dispute where there is strong disagreement
a point asserted as part of an argument

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