An accumulation is a pile or collection of things that has built up gradually over time. When snow falls steadily through the night, each flake adds to the accumulation on the ground until morning reveals several inches of snow. When dust settles on a bookshelf week after week, the accumulation becomes visible and needs cleaning.

A squirrel's accumulation of acorns for winter starts with one nut, then another, then hundreds more tucked into hiding spots. Your accumulation of knowledge about ancient Egypt might begin with one interesting fact about pyramids, then grow through books, documentaries, and museum visits until you know quite a lot.

Scientists study the accumulation of ice in glaciers, which happens over thousands of years as snowfall compresses into thick sheets of ice. Bankers talk about the accumulation of interest in a savings account, where your money grows slowly but steadily. An accumulation of small actions, whether positive or negative, can lead to big results: an accumulation of daily practice makes you skilled, while an accumulation of missed homework assignments can create serious trouble.