by accident

我不小心删除了文件。

I deleted the file ___by ___accident.

我在跳舞时，有人不小心踢到了我，我的眼镜掉了下来。

I was dancing and someone kicked me ___by ___accident, and my glasses fell off.

孩子玩球时不小心打破了窗户。

The child broke the window ___by ___accident while playing ball.