water fountain vs fountain

water fountain and fountain both are nouns.

Word	Noun	Adjective	Verb	Adverb
water fountain	Yes	No	No	No
fountain	Yes	No	No	No

As nouns, fountain is a hypernym of water fountain; that is, fountain is a word with a broader meaning than water fountain:

water fountain: a public fountain to provide a jet of drinking water
fountain: a structure from which an artificially produced jet of water arises

water fountain (noun)	fountain (noun)
a public fountain to provide a jet of drinking water	a plumbing fixture that provides a flow of water
	an artificially produced flow of water
	a structure from which an artificially produced jet of water arises
	a natural flow of ground water