competition vs contestant

competition and contestant both are nouns.

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

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

competition (noun)	contestant (noun)
the act of competing as for profit or a prize	a person who participates in competitions
an occasion on which a winner is selected from among two or more contestants	a person who dissents from some established policy
the contestant you hope to defeat
a business relation in which two parties compete to gain customers