contestant vs player

contestant and player both are nouns.

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

As nouns, player is a hyponym of contestant; that is, player is a word with a more specific, narrower meaning than contestant:

contestant (noun)	player (noun)
a person who participates in competitions	a theatrical performer
a person who dissents from some established policy	a person who participates in or is skilled at some game
	someone who plays a music as a profession
	a person who pursues a number of different social and sexual partners simultaneously
	someone who takes part in an activity