might-have-been vs event

might-have-been and event both are nouns.

Word	Noun	Adjective	Verb	Adverb
might-have-been	Yes	No	No	No
event	Yes	No	No	No

As nouns, event is a hypernym of might-have-been; that is, event is a word with a broader meaning than might-have-been:

might-have-been (noun)	event (noun)
an event that could have occurred but never did	something that happens at a given place and time
	a phenomenon located at a single point in space-time; the fundamental observational entity in relativity theory
	a phenomenon that follows and is caused by some previous phenomenon
	a special set of circumstances