cumulus vs accumulation

cumulus and accumulation both are nouns.

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

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

Other hypernyms of cumulus include aggregation, assemblage, collection.

cumulus (noun)	accumulation (noun)
a collection of objects laid on top of each other	the act of accumulating
a globular cloud	several things grouped together or considered as a whole
	(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

cumulus (adjective)	accumulation (adjective)
of or related to cumulous clouds