一、含义不同
1、Knock on
释义:敲击,结束。
例句:Please do not enter before knocking on the door.
进来前请先敲门。
2、Knock on
释义:敲,撞
例句:Did you hear the knocks at the door?
你听到敲门声了吗?
二、用法不同
1、Knock on
用法:后面可以跟其他物品。
2、knock at
用法:只用于表示敲门。
三、knock at本身就是个固定的词组形式,在表示为敲门或者其它都可以用。
而knockon并不是词组形式,on只是修饰后面跟的名词的介词罢了。
knock at例句:
1、Late that evening, there was a knock at the door.
那天深夜,有人敲过门。
2、Knock at my window at eight o'clock and I'll be ready
8点钟敲我的窗,我会准备好的。
3、I was wakened by a knock at the door.
敲门声把我吵醒了。
knock on例句:
1、He got a nasty knock on the head.
他头部遭到重重一击。
2、He went up the garden path to knock on the door.
他穿过花园小径去敲门。
3、While he was half asleep, he seemed to hear a knock on the door.
矇胧中他仿佛听到有人敲门。