failure vs happening

failure and happening both are nouns.

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

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

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

failure (noun)	happening (noun)
an act that fails	an event that happens
an unexpected omission
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