event vs backwash

event and backwash both are nouns.

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

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

event (noun)	backwash (noun)
something that happens at a given place and time	the wave that spreads behind a boat as it moves forward
a phenomenon located at a single point in space-time; the fundamental observational entity in relativity theory	the flow of air that is driven backwards by an aircraft propeller
a phenomenon that follows and is caused by some previous phenomenon	the consequences of an event (especially a catastrophic event)
a special set of circumstances