accumulation vs step-up

accumulation and step-up both are nouns.

Word	Noun	Adjective	Verb	Adverb
accumulation	Yes	No	No	No
step-up	Yes	No	No	No

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

Other hypernyms of accumulation include increase.

accumulation (noun)	step-up (noun)
the act of accumulating	the act of increasing something
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