hydrant vs fire hydrant

hydrant and fire hydrant both are nouns.

Word	Noun	Adjective	Verb	Adverb
hydrant	Yes	No	No	No
fire hydrant	Yes	No	No	No

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

hydrant: a discharge pipe with a valve and spout at which water may be drawn from the mains of waterworks
fire hydrant: an upright hydrant for drawing water to use in fighting a fire

Other hyponyms of hydrant include fireplug, plug.

hydrant (noun)	fire hydrant (noun)
a discharge pipe with a valve and spout at which water may be drawn from the mains of waterworks	an upright hydrant for drawing water to use in fighting a fire
a faucet for drawing water from a pipe or cask