Definition: as a result of an accident, mistake, etc. Level: B1
他不小心删除了重要文档。
He deleted the important document ___by ___mistake.
孩子玩球时不小心打破了窗户。
The child broke the window ___by ___accident while playing ball.
我误拿了你的伞，以为是我的。
I took your umbrella ___by ___mistake, thinking it was mine.
