堆積

to pile up / to heap / accumulation

to pile up / to heap up / a mass / pile / heap / stack / large amount

to amass / to accumulate / to store / measured quantity (such as area of volume) / product (the result of multiplication) / to integrate (math.) / to solve (or integrate) an ordinary differential equation (math.) / old / long-standing

to pile up like a mountain (idiom) / a mountain of (paperwork etc) / a large number of sth

to play with stacking blocks

face-centered cubic (FCC) (math.)

close-packing of spheres (math.)

hexagonal close-packed (HCP) (math.)