step-up vs accumulation

step-up and accumulation both are nouns.

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

As nouns, accumulation is a hyponym of step-up; that is, accumulation is a word with a more specific, narrower meaning than step-up:

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