累积 (lěi jī): to accumulate

He persisted in studying Chinese for one hour every day; over a year, he accumulated more than two thousand vocabulary words.

By continuously accumulating customer feedback, the company gradually improved its product design.

Staying up late for a long time will accumulate many health problems, such as weakened immunity and memory decline.

This volcano has already accumulated a large amount of magma and could erupt at any time.

She kept all the tickets and photos from every trip; after many years, they accumulated into a thick memoir.