sluice valve vs head gate

sluice valve and head gate both are nouns.

Word	Noun	Adjective	Verb	Adverb
sluice valve	Yes	No	No	No
head gate	Yes	No	No	No

As nouns, sluice valve and head gate are synonyms defined as:

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

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

sluice valve (noun)	head gate (noun)
regulator consisting of a valve or gate that controls the rate of water flow through a sluice	a gate upstream from a lock or canal that is used to control the flow of water at the upper end
	regulator consisting of a valve or gate that controls the rate of water flow through a sluice