1. knock

英語解釋：to repeatedly hit something, producing a noise

knock一般指用拳頭或其他器械猛敲或猛打，也可指用手輕敲某物。

She knocked on the window to attract his attention.

她敲敲窗想引起他的注意。

Theres someone knocking on/at the door.

有人在敲門。

2. tap

英語解釋：to hit something gently, and often repeatedly, especially making short, sharp noises

tap多指慢慢地、連續地輕擊或輕拍。

She tapped her girl to let her sleep.

她輕輕拍著女兒讓她睡覺。

He tapped his forehead knowingly.

他會心地拍拍前額。

3. rap

英語解釋：to hit or say something suddenly and forcefully

rap的本意是敲擊，急拍，指用手指或木棒等迅速地輕敲或急拍，發出刺耳的聲音使大家靜下來。

She rapped the table to get everyones attention.

她敲了敲桌子，讓大伙注意。

The colonel rapped an order to his men.

上校厲聲對他的士兵下命令。

4. pet

英語解釋：If you pet an animal, child, etc., you touch it, him, or her gently and kindly^{1 with your hands.}

pet的意思是溺愛，愛撫，多指溺愛或愛撫動物。

Our dog loves to be petted and tickled^{2 behind the ears.}

大家的狗喜歡人在它耳后愛撫、撓癢。

5. pat

英語解釋：to touch someone or something gently and usually repeatedly with the handflat

pat的意思是輕拍，輕打，指用手輕拍以示同情、同意或撫摸。所以說，我感覺這個詞比較適合描述摸頭殺啦。

He patted my head/patted me on the head tenderly.

他溫順地拍了拍我的頭。