postern vs gate

postern and gate both are nouns.

Word	Noun	Adjective	Verb	Adverb
postern	Yes	No	No	No
gate	Yes	No	Yes	No

As nouns, gate is a hypernym of postern; that is, gate is a word with a broader meaning than postern:

postern (noun)	gate (noun)
a small gate in the rear of a fort or castle	a movable barrier in a fence or wall
	a computer circuit with several inputs but only one output that can be activated by particular combinations of inputs
	passageway (as in an air terminal) where passengers can embark or disembark
	total admission receipts at a sports event

postern (verb)	gate (verb)
	restrict (school boys') movement to the dormitory or campus as a means of punishment
	control with a valve or other device that functions like a gate
	supply with a gate