failure vs occurrence

failure and occurrence both are nouns.

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

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

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

failure (noun)	occurrence (noun)
an act that fails	an event that happens
an unexpected omission	an instance of something occurring
an event that does not accomplish its intended purpose
a person with a record of failing; someone who loses consistently
lack of success
loss of ability to function normally
inability to discharge all your debts as they come due