beginning vs happening

beginning and happening both are nouns.

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

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

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

beginning (noun)	happening (noun)
the act of starting something	an event that happens
the first part or section of something
the event consisting of the start of something
the place where something begins, where it springs into being
the time at which something is supposed to begin

beginning (adjective)	happening (adjective)
serving to begin