mountain vs natural elevation

mountain and natural elevation both are nouns.

Word	Noun	Adjective	Verb	Adverb
mountain	Yes	No	No	No
natural elevation	Yes	No	No	No

As nouns, natural elevation is a hypernym of mountain; that is, natural elevation is a word with a broader meaning than mountain:

mountain: a land mass that projects well above its surroundings; higher than a hill
natural elevation: a raised or elevated geological formation

Other hypernyms of mountain include elevation.

mountain (noun)	natural elevation (noun)
a land mass that projects well above its surroundings; higher than a hill	a raised or elevated geological formation
(often followed by `of') a large number or amount or extent