compost pile vs heap

compost pile and heap both are nouns.

Word	Noun	Adjective	Verb	Adverb
compost pile	Yes	No	No	No
heap	Yes	No	Yes	No

As nouns, heap is a hypernym of compost pile; that is, heap is a word with a broader meaning than compost pile:

compost pile: a heap of manure and vegetation and other organic residues that are decaying to become compost
heap: a collection of objects laid on top of each other

Other hypernyms of compost pile include agglomerate, cumulation, cumulus, mound, pile.

compost pile (noun)	heap (noun)
a heap of manure and vegetation and other organic residues that are decaying to become compost	a car that is old and unreliable
	a collection of objects laid on top of each other
	(often followed by `of') a large number or amount or extent