bettor vs gambler

bettor and gambler both are nouns.

Word	Noun	Adjective	Verb	Adverb
bettor	Yes	No	No	No
gambler	Yes	No	No	No

As nouns, gambler is a hypernym of bettor; that is, gambler is a word with a broader meaning than bettor:

bettor: someone who bets
gambler: a person who wagers money on the outcome of games or sporting events

bettor (noun)	gambler (noun)
someone who bets	a person who wagers money on the outcome of games or sporting events
	someone who risks loss or injury in the hope of gain or excitement