This is Everyday Grammar. I'm Kaveh.
And I'm Lucija. Today we're going to talk about using modals to ask for permission.
Hey Lucija. I need to pick up my sister from the airport. Can I drive your car?
I don't know. Can you drive my car? It's a manual transmission.
That's not what I meant, silly. Of course I can drive a manual transmission.
But you did bring up an important grammar point. Can is a confusing modal verb. Traditionally can expresses ability. But today, a lot of people use can to ask for permission, which is fine. But it's not always clear if someone is asking about ability or asking for permission.
Well, can you give me an example?
It's hot in here. Can I open the window?
It's hot in here. Can I open the window?（这儿很热，我能开窗吗？）
I don't know. Can you? Are you asking if it is possible to open the window? Or are you asking for permission to open the window.
I'm asking for permission. But we have other options. May I is a clear and very polite way to ask for permission.
OK, so let's go back to my first question. May I drive your car?
Good. Now it is clear that you are asking for permission. But may is rather formal. Could is less formal and a better choice to use with friends.
Could I drive your car to the airport?
And that's Everyday Grammar.