成千上万

chéng qiān shàng wàn

thousands upon thousands

Character by character

成chéng
reach

千qiān
thousands

上shàng
up to

万wàn
ten thousands

成千上万的人参加了这次活动。

Thousands upon thousands of people took part in the event.

Tone: neutral.

Usually 成千上万的 + noun, for a vague but huge number.

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