以为 (yǐ wéi): 생각하다; 믿다 (종종 그 믿음이 잘못되었다는 함의를 가짐 – 자신의 현재 믿음을 언급하는 경우는 제외); 생각하다 (종종 잘못); 믿다; 가정하다

I thought you had already left yesterday.

He thought it would rain today, but it turned out to be a sunny day.

Don't think that I don't know about this.

I originally thought this task was very simple, but actually it's very difficult.