event vs aftermath

event and aftermath both are nouns.

Word	Noun	Adjective	Verb	Adverb
event	Yes	No	No	No
aftermath	Yes	No	No	No

As nouns, aftermath is a hyponym of event; that is, aftermath is a word with a more specific, narrower meaning than event:

event (noun)	aftermath (noun)
something that happens at a given place and time	the outcome of an event especially as relative to an individual
a phenomenon located at a single point in space-time; the fundamental observational entity in relativity theory	the consequences of an event (especially a catastrophic event)
a phenomenon that follows and is caused by some previous phenomenon
a special set of circumstances