event vs by-product

event and by-product both are nouns.

Word	Noun	Adjective	Verb	Adverb
event	Yes	No	No	No
by-product	Yes	No	No	No

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

event (noun)	by-product (noun)
something that happens at a given place and time	a product made during the manufacture of something else
a phenomenon located at a single point in space-time; the fundamental observational entity in relativity theory	a secondary and sometimes unexpected consequence
a phenomenon that follows and is caused by some previous phenomenon
a special set of circumstances