Can – permission 可以 kěyǐ

可以 kěyǐ

可以 kěyǐ refers to permission or the ability to do something in a given situation. It is often used to make requests or ask for permission, and can also be used to describe what is allowed or permissible in a particular context.It is similar in meaning to the English phrases “may I” or “could you” in an interrogative sentence (question sentence).

我wǒ可以kěyǐ說shuō英文yīngwén嗎ma? 我wǒ可以kěyǐ说shuō英文yīngwén吗ma?
May I speak English?

不bù可以kěyǐ拍照pāizhào不bù可以kěyǐ拍照pāizhào
No photos allowed.

請問qǐngwèn可以kěyǐ借jiè我wǒ手機shǒujī嗎ma？ 请问qǐngwèn可以kěyǐ借jiè我wǒ手机shǒujī吗ma？
May I borrow your cell phone?

Intermediate Level

THE OVERLAPPING PART

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能 néng and 可以 kěyǐ

Both 能 néng and 可以 kěyǐ can be used to express possibility:

你nǐ今天jīntiān能néng/ 可以kěyǐ來lái我家wǒjiā嗎ma? 你nǐ今天jīntiān能néng/ 可以kěyǐ来lái我家wǒjiā吗ma?
Can you come to my place today?
(Is it possible for you to come to my place today?)

你nǐ能néng/ 可以kěyǐ把bǎ鹽yán遞dì給gěi我wǒ嗎ma？ 你nǐ能néng/ 可以kěyǐ把bǎ盐yán递dì给gěi我wǒ吗ma？
Can you pass the salt to me?

你nǐ能néng/ 可以kěyǐ說shuō慢màn一點yìdiǎn嗎ma？ 你nǐ能néng/ 可以kěyǐ说shuō慢màn一点yìdiǎn吗ma？
Can you say it a little slower?

你nǐ能néng/ 可以kěyǐ閉嘴bìzuǐ嗎ma？ 你nǐ能néng/ 可以kěyǐ闭嘴bìzuǐ吗ma？
Could you shut up?

However, when you want to express impossibility in Chinese, 不能 bùnéng is the only choice.

我wǒ今天jīntiān很hěn忙máng， 不能bùnéng去qù你家nǐjiā我wǒ今天jīntiān很hěn忙máng， 不能bùnéng去qù你家nǐjiā
I am quite busy today, so I can’t go to your place.
(No possible)

我wǒ今天jīntiān很hěn忙máng， 不bù可以kěyǐ去qù你家nǐjiā我wǒ今天jīntiān很hěn忙máng， 不bù可以kěyǐ去qù你家nǐjiā (X)
I am quite busy today, so I can’t go to your place.
(If you use 不可以, it implies someone not allowed you to go.)

我媽wǒmā說shuō太tài晚wǎn了le， 今天jīntiān不可以bùkěyǐ去qù你家nǐjiā我妈wǒmā说shuō太tài晚wǎn了le， 今天jīntiān不可以bùkěyǐ去qù你家nǐjiā
My mom said it’s too late, so I can’t go to your place today.
(You are not allowed to)

Both 能 néng and 可以 kěyǐ can be used to express restore ability: 

經過jīngguò手術shǒushù後hòu， 我wǒ又yòu能néng/ 可以kěyǐ走路zǒulù了le经过
After the surgery, I could walk again!