fountain vs bubbler

fountain and bubbler both are nouns.

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

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

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

Other hyponyms of fountain include drinking fountain, water fountain.

fountain (noun)	bubbler (noun)
a plumbing fixture that provides a flow of water	a public fountain to provide a jet of drinking water
an artificially produced flow of water	any of various devices in which air or some other gas is bubbled through a liquid
a structure from which an artificially produced jet of water arises
a natural flow of ground water