appearance vs happening

appearance and happening both are nouns.

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

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

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

appearance (noun)	happening (noun)
the act of appearing in public view	an event that happens
formal attendance (in court or at a hearing) of a party in an action
pretending that something is the case in order to make a good impression
outward or visible aspect of a person or thing
a mental representation
the event of coming into sight