floodgate vs head gate

floodgate and head gate both are nouns.

Word	Noun	Adjective	Verb	Adverb
floodgate	Yes	No	No	No
head gate	Yes	No	No	No

As nouns, floodgate and head gate are synonyms defined as:

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

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

floodgate (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
something that restrains a flood or outpouring	regulator consisting of a valve or gate that controls the rate of water flow through a sluice