lottery vs chance event

lottery and chance event both are nouns.

Word	Noun	Adjective	Verb	Adverb
lottery	Yes	No	No	No
chance event	Yes	No	No	No

As nouns, chance event is a hypernym of lottery; that is, chance event is a word with a broader meaning than lottery:

lottery: something that is regarded as a chance event
chance event: anything that happens suddenly or by chance without an apparent cause

Other hypernyms of lottery include accident, fortuity, stroke.

lottery (noun)	chance event (noun)
players buy (or are given) chances and prizes are distributed by casting lots	anything that happens suddenly or by chance without an apparent cause
something that is regarded as a chance event