instance vs occurrence

instance and occurrence both are nouns.

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

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

Other hypernyms of instance include happening, natural event, occurrent.

instance (noun)	occurrence (noun)
an item of information that is typical of a class or group	an event that happens
an occurrence of something	an instance of something occurring

instance (verb)	occurrence (verb)
clarify by giving an example of