表示能力

I can readItalian, but I can’t speak it.

Dogs can’tclimb trees.

表示可能性， 比如能去还是不能去，

We can go to suzhou thisweekend, because I don’t have to work.

I can’t come out thisevening: I have to see my brother.

I usuallyvisit my grandparent every Saturday. But this Saturday my grandparents will notbe at home. So I can go out with you.

can / may  请求允许，可以换用

CanI borrow your pen?  May I borrow your pen?

Yes, youcan. Sorry I'm afraid that you can't.

May I come in?  

You may come in ifyou wish.

表示概率（chance） 

Youmay be right; We may go shopping.

 ‘Where’s Emma?’‘I don’t know. She might be out running, I suppose.’

 ‘I think it’s going to rain.’‘You may well beright – the sky’s really black.’

否定的用法，注意区别

She may be at home.(= Perhaps she is at home.)

She may not be athome. (= Perhaps she is not at home.)

She can’t be athome. (= She is certainly not at home.)