Asking for permission

 We use  can, could, may and  might to ask for permission, depending on the situation.

1.  Can is the commonest and most informal: Can I borrow your umbrella (please)?
2.  Could is more polite than can: Could I borrow your umbrella (please)?
3.  May is more formal, more respectful than can and could: May I borrow your umbrella (please)?
4.  Might is the most polite but the least common: Might I borrow your umbrella (please)?
5.  We can add possibly and use the expressions like Do you think and  I wonder if to make requests even more polite.

Can/Could/May/Might I possibly borrow your umbrella?
Do you think I could/Do you think I might (possibly) borrow your umbrella?
I wonder if I could/I wonder if I might (possibly) borrow your umbrella?

Giving and refusing permission

We use can or may to give permission (but not could or might). May is formal and not often used in speech.

• You can wait in my office if you like. Could I borrow your calculator? — Of course you can. You may watch TV for as long as you like.

To refuse permission we use the negative forms.

• I'm sorry, but you can't picnic here. Members may not bring more than two visi­tors into the club.

 We can also use must not.

• Bicycles may not (OR must not) be left here.

Talking about permission

We sometimes talk about rules made by someone else. To do this we use can, could and be allowed to. We use can to talk about the present or the future, and we use could for the past:

Present:   Each passenger can take one bag onto the plane.
Future:     I can't have another day off tomorrow.
Past:         Years ago you could park your car anywhere.

We can also use be allowed to:

Present:   Passengers are allowed to take one bag onto the plane.
Future:    Will I be allowed to record the interview on tape?
Past: We weren't allowed to feed the animals at the zoo yesterday.

For a general permission in the past we use either could or was/were allowed to:

• I could always stay (OR I was allowed to stay) up late as a child.

But we cannot use could when we mean that an action really happened at a time in the past.

• I was allowed to leave work early yesterday. (Not: I could leave ...)

This is like the difference between could and was/ were able to.

Compare questions with may and be allowed to:

May I take a photo of you?
(Asking for permission: 'Will you allow it?')
Are we allowed to take photos?
(Asking about permission: 'What is the rule?')