occurrence vs event

occurrence and event both are nouns.

Word	Noun	Adjective	Verb	Adverb
occurrence	Yes	No	No	No
event	Yes	No	No	No

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

occurrence (noun)	event (noun)
an event that happens	something that happens at a given place and time
an instance of something occurring	a phenomenon located at a single point in space-time; the fundamental observational entity in relativity theory
	a phenomenon that follows and is caused by some previous phenomenon
	a special set of circumstances