可以 is not always can

可以 is often taught as "can". That works sometimes, but it hides the social range of the word. In real Mandarin, 可以 can mean "can", "may", "is okay", "works", or "is acceptable".

That makes it one of the most practical words in daily speech.

Permission: may I do this?

If you ask May I come in?, you are not asking whether your legs are physically able to enter. You are asking for permission. 可以 here means "may I" or "is it okay if I".

This is why 可以 shows up in polite requests:

• 可以借我一下嗎?
• 可以慢一點嗎?
• 可以再說一次嗎?

Acceptability: does this work?

可以 also checks whether something is acceptable. Is this okay? is one of the most useful Mandarin questions. It can mean "Is this okay?", "Will this work?", or "Is this acceptable?"

The answer 可以 may mean "yes, that works", not "yes, it has the ability".

Soft refusal: not really possible

When someone says Today is not really good, they are often refusing gently. The literal words are about possibility, but the social message is "today does not really work".

This is why 可以 is not only grammar. It is also politeness. A direct "no" can feel heavy, so speakers often talk about whether something is possible or acceptable instead.

As a learner, treat 可以 as a flexible "works or is allowed" word. That will help you understand more real conversations than the simple translation "can".