challenger vs contender

challenger and contender both are nouns.

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

As nouns, challenger and contender are synonyms defined as:

Other synonyms of challenger include competition, competitor, rival.

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