challenger vs rival

challenger and rival both are nouns.

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

As nouns, challenger and rival are synonyms defined as:

Other synonyms of challenger include competition, competitor, contender.

challenger (noun)	rival (noun)
the contestant you hope to defeat	the contestant you hope to defeat

challenger (adjective)	rival (adjective)
	as a rival in a competition

challenger (verb)	rival (verb)
	be the rival of, be in competition with
	be equal to in quality or ability