mountain vs ben

mountain and ben both are nouns.

Word	Noun	Adjective	Verb	Adverb
mountain	Yes	No	No	No
ben	Yes	No	No	No

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

mountain: a land mass that projects well above its surroundings; higher than a hill
ben: a mountain or tall hill

Other hyponyms of mountain include alp, seamount, volcano.

mountain (noun)	ben (noun)
a land mass that projects well above its surroundings; higher than a hill	a mountain or tall hill
(often followed by `of') a large number or amount or extent