backlog vs accumulation

backlog and accumulation both are nouns.

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

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

backlog: an accumulation of jobs not done or materials not processed that are yet to be dealt with (especially unfilled customer orders for products or services)
accumulation: several things grouped together or considered as a whole

Other hypernyms of backlog include aggregation, assemblage, collection.

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

backlog: something kept back or saved for future use or a special purpose
accumulation: (finance) profits that are not paid out as dividends but are added to the capital base of the corporation

backlog (noun)	accumulation (noun)
an accumulation of jobs not done or materials not processed that are yet to be dealt with (especially unfilled customer orders for products or services)	the act of accumulating
something kept back or saved for future use or a special purpose	several things grouped together or considered as a whole
the large log at the back of a hearth fire	(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

backlog (verb)	accumulation (verb)
accumulate and create a backlog