accumulate + -ation

source: bandai GIF - Find & Share on GIPHY

the acquisition or gradual gathering of something: 何かの収集物、徐々に集めること

蓄積, 積み重ね; 利殖; 蓄積物, たまった物

e.g. the accumulation of wealth.: 富の蓄積

a mass or quantity of something that has gradually gathered or been acquired: 徐々に集められた、入手されたものの集まり、量

e.g. the accumulation of paperwork on her desk.: 彼女の机の上の書類の山