Form of modals and related verbs: permission/prohibition

can/could/may/might [compare > 11.34, 11.36-38]:
Can I stay out late? you (etc.) can/can't/mustn't stay out late

Could I stay out late?

May I stay out late? you (etc.)may/may not/mayn't/mustn't stay out late Might I stay out late?

can/could (= be free to) present or future reference:

/ can see him now/tomorrow

I could see him now/tomorrow

Verbs and verb phrases related in meaning to can/could/may/might/mustn't

(not) be allowed to. You're (not) allowed to stay out late

(not) be permitted to. You're (not) permitted to stay out late

be forbidden to: You're forbidden to stay out late

be prohibited. Smoking is (strictly) prohibited

be not to: You 're not to smoke

negative imperative: Don't smoke¹

11 Modal auxiliaries and related verbs

11.20 Asking for permission/responding: 'can/could/may/might'

Requests for permission can be graded on a 'hesitancy scale’, ranging from a blunt request to an extremely hesitant one. Requests for permission can refer to the present or future. The basic forms are:

Can

Could I borrow your umbrella (please)'?

May

Might

1 Can is the commonest and most informal:
Can I borrow your umbrella (please)?

A few (old-fashioned) native speakers still hold that can is the equivalent of am/is/are able to and therefore may must be used instead. The idea of e.g. asking for a favour is less strong in can than in could/may/might.

2 Could is more 'hesitant' and polite than can. We often use it when we are not sure permission will be granted: Could I borrow your umbrella (please)?

3 May is more formal, polite and 'respectful' than can and could: May I borrow your umbrella (please)?

4 Might is the most hesitant, polite and 'respectful' and is rather less common than the other three: Might I borrow your umbrella (please)?

In practice, can, could and may are often interchangeable in 'neutral' requests.

Common responses with modals are: e.g.

- affirmative: Of course you can/may. (Not "could*/'might")

- negative: No, you can't/may not. (Not "could not"/"might not")

Numerous non-modal responses are possible ranging from the polite Of course (affirmative), I'm afraid not, I'd rather you didn't (negative), to blunt refusal like Certainly not. A polite refusal is usually accompanied by some kind of explanation (I'm afraid you can't because.).

Permission to ask an indiscreet question may be requested with the formulas if I may ask and (more tentative) if I might ask: How much did you pay for this house if I may/might ask?

11.21 Asking for permission with 'can't' and 'couldn't'

Can't and couldn't are often used in place of can and could when we are pressing for an affirmative answer [> 13.6]:

can't I stay out till midnight (please)?
Couldn't

May I not? is old-fashioned.

Mayn't I? is unlikely.

Might I not.? is rare, but all these forms occur in formal style.

Modals, etc to express permission/prohibition

11.22 Very polite requests: 'can/could/may/might'

There are numerous variations on straightforward request forms to express degrees of politeness. Possibly is commonly added to make requests more polite. Requests may be hesitant:

Can/Could I (possibly)

Do you think I could/might use your phone?