Modals - permission and obligation

Modals - permission and obligation

1. modal verbs to speak of permission and obligation

   • examples
     • can, can't
       • You can put your shoes and coat over there. You can't leave your bike there.
     • must, mustn't
       • I must call the electrician and get that light fixed. You mustn't worry about me. I'll be fine.
     • have to and don’t have to
       • You have to have a licence to drive a car. You don't have to have a licence to cycle on the roads.

2. Grammar explanation

   • We often use verbs with modal meanings to talk about permission and obligation.
     • Permission
       • can
         • We often use can to ask for and give permission.
           • Can I sit here? You can use my car if you like. Can I make a suggestion?
       • could
         • We also use could to ask for permission (but not to give it). Could is more formal and polite than can.
           • Could I ask you something? Could I interrupt? Could I borrow your pen for a moment, please?
       • may
         • May is the most formal way to ask for and give permission.
           • May I see your passport, please? Customers may request a refund within a period of 30 days. These pages may be photocopied for classroom use.
     • Prohibition
       • We use can't and mustn't to show that something is prohibited – it is not allowed.
         • can't
           • We use can't to talk about something that is against the rules, particularly when we didn't make the rules.
             • What does this sign say? Oh, we can't park here. You can't take photos in the museum. They're really strict about it. Sorry, we can't sell knives to under-18s.
         • must not/mustn't
           • We use must not to talk about what is not permitted. It is common on public signs and notices informing people of rules and laws.
             • Visitors must not park in the staff car park. Baggage must not be left unattended. Guests must not make noise after 10 p.m.
             • We use mustn't particularly when the prohibition comes from the speaker.
               • (Parent to child) You mustn't say things like that to your sister. (Teacher to student) You mustn't be late to class.
     • Obligation
       • We use have to and must to express obligation. There is a slight difference between the way we use them.
         • have to
           • Have to shows us that the obligation comes from outside the speaker.
             • We have to wear a uniform when we're working in reception. (Student to teacher) When do we have to hand in our homework?
         • must
           • Must expresses a strong obligation or necessity. It often shows us that the obligation comes from the speaker (or the authority that wrote the sentence).
             • (Teacher to student) You must hand in your homework on Tuesday or you will lose ten per cent of your mark. (Sign on a plane) Seat belts must be worn by all passengers.
         • No obligation
           • don't have to
             • We use don’t have to to show that there is no obligation. You can do something if you want to but it's not compulsory.
               • ou don't have to go to the bank to do a transfer. You can do it online. You don't have to come with me, honestly. I'll be fine!