reservoir vs sump

reservoir and sump both are nouns.

Word	Noun	Adjective	Verb	Adverb
reservoir	Yes	No	No	No
sump	Yes	No	No	No

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

Other hyponyms of reservoir include cistern, water tower.

reservoir (noun)	sump (noun)
tank used for collecting and storing a liquid (as water or oil)	a well or other hole in which water has collected
lake used to store water for community use; a lake (natural or artificial) used to store water and used as a source of water	an oil reservoir in an internal combustion engine
anything (a person or animal or plant or substance) in which an infectious agent normally lives and multiplies	a covered cistern; waste water and sewage flow into it
a large or extra supply of something