penstock vs floodgate

penstock and floodgate both are nouns.

Word	Noun	Adjective	Verb	Adverb
penstock	Yes	No	No	No
floodgate	Yes	No	No	No

As nouns, penstock and floodgate are synonyms defined as:

penstock and floodgate: regulator consisting of a valve or gate that controls the rate of water flow through a sluice

Other synonyms of penstock include head gate, sluice valve, sluicegate, water gate.

penstock (noun)	floodgate (noun)
conduit that carries a rapid flow of water controlled by a sluicegate	regulator consisting of a valve or gate that controls the rate of water flow through a sluice
regulator consisting of a valve or gate that controls the rate of water flow through a sluice	something that restrains a flood or outpouring