英语释义： to repeatedly hit something, producing a noise
She knocked on the window to attract his attention.
There's someone knocking on/at the door.
英语释义：to hit something gently, and often repeatedly, especially making short, sharp noises
She tapped her girl to let her sleep.
He tapped his forehead knowingly.
英语释义： to hit or say something suddenly and forcefully
She rapped (on) the table to get everyone's attention.
The colonel rapped (out) an order to his men.
英语释义：If you pet an animal, child, etc., you touch it, him, or her gently and kindly with your hands.
Our dog loves to be petted and tickled behind the ears.
英语释义：to touch someone or something gently and usually repeatedly with the handflat
He patted my head/patted me on the head tenderly.