challenge vs challenger

challenge and challenger both are nouns.

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

challenge (noun)	challenger (noun)
a call to engage in a contest or fight	the contestant you hope to defeat
questioning a statement and demanding an explanation
a formal objection to the selection of a particular person as a juror
a demand by a sentry for a password or identification
a demanding or stimulating situation

challenge (verb)	challenger (verb)
issue a challenge to
take exception to
raise a formal objection in a court of law
ask for identification