heap vs accumulation

heap and accumulation both are nouns.

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

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

Other hypernyms of heap include aggregation, assemblage, collection.

heap (noun)	accumulation (noun)
a car that is old and unreliable	the act of accumulating
a collection of objects laid on top of each other	several things grouped together or considered as a whole
(often followed by `of') a large number or amount or extent	(finance) profits that are not paid out as dividends but are added to the capital base of the corporation
	an increase by natural growth or addition