side effect vs event

side effect and event both are nouns.

Word	Noun	Adjective	Verb	Adverb
side effect	Yes	No	No	No
event	Yes	No	No	No

As nouns, event is a hypernym of side effect; that is, event is a word with a broader meaning than side effect:

Other hypernyms of side effect include consequence, effect, issue, outcome, result, upshot.

side effect (noun)	event (noun)
any adverse and unwanted secondary effect	something that happens at a given place and time
a secondary and usually adverse effect of a drug or therapy	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