contender vs challenger

contender and challenger both are nouns.

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

As nouns, contender and challenger are synonyms defined as:

Other synonyms of contender include competition, competitor, rival.

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