Look at these examples to see how can, can't, must, mustn't, have to and don’t have to are used.
You can put your shoes and coat over there.
You can't leave your bike there.
I must call the electrician and get that light fixed.
You mustn't worry about me. I'll be fine.
You have to have a licence to drive a car.
You don't have to have a licence to cycle on the roads.
Try this exercise to test your grammar.
- Grammar test 1
Read the explanation to learn more.
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.
I mustn't let that happen again.
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?
Al has to work tomorrow so he can't come.
We sometimes call this 'external obligation'.
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).
I must phone my dad. It's his birthday today.
(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.
Note that we don't use must to express obligation in the past. We use have to instead.
I had to pay £85 to renew my passport last week.
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.
You don't have to wear a tie in our office but some people like to dress more formally.
You 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!
Do this exercise to test your grammar again.
- Grammar test 2
LearnEnglish team,
I would like to know the difference between can you, could you, will you, and would you?
I think these are not models of permission and application these are models of requests. How to use these models of requests in a grammatically acceptable way?
Thank you very much.
Hello ShetuYogme,
As you say, these are all phrases which can be used for requests. In terms of structure they are all followed by a bare infinitive. In terms of use as requests they are very similar in meaning with really only a difference in politeness/formality. You can read more and see more examples on these pages:
https://dictionary.cambridge.org/grammar/british-grammar/requests
https://learnenglish.britishcouncil.org/grammar/english-grammar-reference/requests-offers-invitations
Peter
The LearnEnglish Team
Hi again,
Can and will are informal; and; could and would are formal. If so, I would like to know the difference between
Thank you.
Hello again ShetuYogome,
The difference is small and in many situations you can choose between the pairs.
Can and could ask if something is possible. A person may be happy to do something but not have the time, for example.
Will and would ask if the other person agrees to something. A person may have the time but not be willing to do something, for example.
Peter
The LearnEnglish Team
Hello Team. Could you please help me? I think all the first three options are correct but I need your support.
Choose: "You have to be quiet in class," said .......... .
a) the head teacher b) a schoolmate c) the student sitting next to me d) b & c
Thank you
Hi Ahmed Imam,
I agree with you. There are tendencies for "must" to express an obligation from the authority of the speaker, and for "have to" to express an obligation from an authority outside the speaker. So, we might typically expect the head teacher to say "You must be quiet in class", for example, since the head teacher has high authority in the school. However, those are tendencies rather than fixed rules, and it's not wrong for the head teacher to say "have to". Perhaps the head teacher feels that the rules come not from him/herself but from something else (from the school, for example), or perhaps he/she felt in that moment that "must" was too strong and preferred a lighter-sounding word.
There is an overlap in usage of "have to" and "must" - that is, situations where both are acceptable and used. I would say that this example is one of those situations.
Jonathan
LearnEnglish team
Hello, I didn't understand 2 examples of on the website.
First example is "You...be a member to buy a ticket. It's open to everyone."
In this sentense why didn't we use "can"?
Second example is "The hostel is totally vegetarian. You...cook or eat meat there."
In this example why didn't we use "don't have to"?
Hi nurserin,
Thanks for your questions!
First, I want to clarify the meaning of "don't have to". It means "it is not necessary", or "it is optional". For example, I can say "I don't have to wear a suit at work", which means I can wear a suit if I want, but there is no obligation to wear a suit. Don't confuse it with "can't", which means "it is not OK" or "it is not allowed".
In the first example, it says "It's open to everyone". So, the main point is that it is not for members only, but also non-members. That's why "don't have to" is the best answer ("You don't have to be a member" = "It is not necessary to be a member" or "There is no obligation to be a member").
Since everyone can buy a ticket, it's true to say "You can be a member to buy a ticket". However, the main point is that everyone can buy a ticket, not just members but non-members too.
In the second example, "don't have to" isn't right because "don't have to" means "it is not necessary". It would be strange for cooking/eating meat in the hostel to be "necessary". Instead, the point is that it's not OK or not allowed to cook/eat meat there (because it's a vegetarian hostel). It's not OK to do that, even if you want to. So, the answer is "can't", which shows something is not allowed or not OK.
Does that make sense?
Jonathan
LearnEnglish team
Hi, I am confused about using used to and must not. So as far as I understood we can both use must not and cannot for prohibitions. Can you check these examples.
It is not permitted to enter the construction site without a hard hat.
→ You ......... enter the construction site without a hard hat.
It is not allowed to take pictures inside the concert hall.
→ You ........... take pictures inside the concert hall.
It is prohibited to bring outside food into the theme park.
→ You ......... bring outside food into the theme park.
I couldn't decide if they are can't or musn't. Can you explain please?
Hello zeynepkaya,
It is possible to use both 'can't' and 'mustn't' in this sentences. But since they seem to be sentences spoken by someone who is telling another person about the restrictions, it would be more natural to use 'can't'.
In other words, we tend to use 'can't' when we are reporting about restrictions. But on signs or when an authority figure (e.g. an usher in the concert hall or a theme park employee) is speaking, we often use 'mustn't'.
Best wishes,
Kirk
LearnEnglish team