participant vs contestant

participant and contestant both are nouns.

Word	Noun	Adjective	Verb	Adverb
participant	Yes	No	No	No
contestant	Yes	No	No	No

As nouns, contestant is a hypernym of participant; that is, contestant is a word with a broader meaning than participant:

participant (noun)	contestant (noun)
someone who takes part in an activity	a person who participates in competitions
a person who participates in or is skilled at some game	a person who dissents from some established policy