mountain vs heap

mountain and heap both are nouns.

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

As nouns, mountain and heap are synonyms defined as:

mountain and heap: (often followed by `of') a large number or amount or extent

mountain (noun)	heap (noun)
a land mass that projects well above its surroundings; higher than a hill	a car that is old and unreliable
(often followed by `of') a large number or amount or extent	a collection of objects laid on top of each other
	(often followed by `of') a large number or amount or extent