overflow vs effusion

overflow and effusion both are nouns.

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

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

overflow (noun)	effusion (noun)
a large flow	flow under pressure
the occurrence of surplus liquid (as water) exceeding the limit or capacity	an unrestrained expression of emotion

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