crack

She opened the door a crack and peeped into the room.

她把门打开一条缝，往房间里偷看。

There was a sharp crack as the branch broke off.

树枝咔嚓一声折断了。

Don’t put boiling water in the glass or it will crack.

不要把沸水倒进这个玻璃杯里，否则它会破裂的。