rival vs champion

rival and champion both are nouns.

Word	Noun	Adjective	Verb	Adverb
rival	Yes	Yes	Yes	No
champion	Yes	Yes	Yes	No

As nouns, champion is a hyponym of rival; that is, champion is a word with a more specific, narrower meaning than rival:

rival (noun)	champion (noun)
the contestant you hope to defeat	someone who fights for a cause
	someone who has won first place in a competition
	a person who backs a politician or a team etc.
	someone who is dazzlingly skilled in any field

rival (adjective)	champion (adjective)
as a rival in a competition	holding first place in a contest

rival (verb)	champion (verb)
be the rival of, be in competition with	protect or fight for as a champion
be equal to in quality or ability