overflow vs runoff

overflow and runoff both are nouns.

Word	Noun	Adjective	Verb	Adverb
overflow	Yes	No	Yes	No
runoff	Yes	No	No	No

As nouns, overflow and runoff are synonyms defined as:

overflow and runoff: the occurrence of surplus liquid (as water) exceeding the limit or capacity

Other synonyms of overflow include overspill.

overflow (noun)	runoff (noun)
a large flow	a final election to resolve an earlier election that did not produce a winner
the occurrence of surplus liquid (as water) exceeding the limit or capacity	the occurrence of surplus liquid (as water) exceeding the limit or capacity

overflow (verb)	runoff (verb)
overflow with a certain feeling
flow or run over (a limit or brim)