1）Generally speaking: may means being allowed to do something, while can means having the ability to do something.
He can swim the channel.
He can swim across the strait.
Children may swim in the pool only when there is a lifeguard present.
Children can only swim in the pool when a lifeguard is present.
However, in practical usage, can often encroaches on the usage of may.
You can go when I dismiss the class, but no sooner.
You can leave when I announce the end of the class, but you cannot leave before that.
Sometimes this can cause ambiguity.
You can walk to the theatre.
You can walk to the theatre. Or: You are allowed to walk to the theatre.
The context needs to be used to determine.
2）If someone politely asks: May I use the telephone?
It’s better not to respond: Yes, you may. This sounds a bit condescending (the person used may to be humble, and responding with their humility makes it sound arrogant). It’s better to say:
Yes, of course you can.
3）When making a statement about objective possibility, only may, might, or could can be used, not can.
4）When making a statement about objective possibility in the negative, may or can can be used, but the meanings differ: may not means “might not,” while cannot means “impossible.”
She may not be at home.
She might not be at home.
She cannot be at home.
She cannot be at home.
5）When stating what someone else might do (that is, announcing permission), both may and can can be used. However, if objectively stating that someone has been allowed to do something, may cannot be used (and might cannot be used for the past), you must use can or be allowed to.
These days, children can/ are allowed to do what they like.
These days, children can do whatever they want.
I could/ was allowed to read what I liked when I was a child.
I could read whatever I wanted when I was a child.
Can/ Are you allowed to park on both sides of the road here?
Is it allowed to park on both sides of the road here?
If indirectly reporting someone announcing permission, may can be used.
The manager says that we may leave our coats in the downstairs toilet.
The manager says we can leave our coats in the downstairs restroom.
Related Topics:
——”Can”