ACCUMULATE

[verb] - to collect a large number of (things) over a long period of time, or to gradually increase in number or amountAs people accumulate more wealth, they tend to spend a greater proportion of their incomes. [T]The company said the debt was accumulated during its acquisition of nine individual businesses. [T]We've accumulated so much rubbish over the years. [T]A thick layer of dust had accumulated in the room. [I]If you don't sort out the papers on your desk on a regular basis they just keep on accumulating. [I]