lottery vs sweepstakes

lottery and sweepstakes both are nouns.

Word	Noun	Adjective	Verb	Adverb
lottery	Yes	No	No	No
sweepstakes	Yes	No	No	No

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

lottery: players buy (or are given) chances and prizes are distributed by casting lots
sweepstakes: a lottery in which the prize consists of the money paid by the participants

Other hyponyms of lottery include tombola, lucky dip, numbers, numbers game, numbers pool, numbers racket, raffle.

lottery (noun)	sweepstakes (noun)
players buy (or are given) chances and prizes are distributed by casting lots	a lottery in which the prize consists of the money paid by the participants
something that is regarded as a chance event