chance event vs occurrent

chance event and occurrent both are nouns.

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

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

chance event: anything that happens suddenly or by chance without an apparent cause
occurrent: an event that happens

Other hypernyms of chance event include happening, natural event, occurrence.

chance event (noun)	occurrent (noun)
anything that happens suddenly or by chance without an apparent cause	an event that happens

chance event (adjective)	occurrent (adjective)
	presently occurring (either causally or incidentally)