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
Hello noorav,
This is not a question for this site, I'm afraid. This site is for language learners; you need a site for people studying linguistics for this kind of question.
I recommend the appropriate section of StackExchange:
https://english.stackexchange.com
Good luck with your test!
Peter
The LearnEnglish Team
Hello,
Please, could you explain which of the two grammatical structures is correct?
Wouldn't it be better to turn the written text into graphics?
or
Would it not be better to turn the written text into graphics?
Thanks a lot
Hi User_1,
Actually, they are both correct!
Jonathan
LearnEnglish team
Jonathan, thanks a lot
Hi,
I came across with the word CAN NOT separated. Is it correct? I would like to know if the negative form of CAN is only CANNOT or we can use CAN NOT, and if so when we can use CAN NOT form? Thanks.
Tony
Hi Tony,
Thanks for your question! It should be a single word, cannot. Although people do sometimes write can not, it is an error. There is one exception - if "not" describes another verb, instead of "can", e.g. I don't mind if you don't want to go to the park. We can not go." (meaning = "we do not need to go" or "it's fine if we do not go"; "not" describes "go", not "can").
I hope that helps.
Jonathan
LearnEnglish team
Hi LearnEnglish team,
I would like ask about the use of "have to" in the past perfect tense. Would you please supply some examples?
Hello Rabearabea,
'I'd had to make a few calls before I could start writing' or 'She'd had to try six times before she got the car started' are a couple of examples. It's a little unusual in the past perfect, but definitely possible.
All the best,
Kirk
LearnEnglish team
Thank you LearnEnglish team ( Kirk ) for your reply about the past perfect of "have to" but I came cross a strange grammatical rule in a text book of English for EFL. The rule says that the past perfect of "have to " is " have had to" ,e.g.
I have never had to go to hospital. (past perfect)
Would you please explain if this rule is correct?
Hi Rabearabea,
Sorry, that's incorrect. "Have had to" is the present perfect, not past perfect. It uses "have" as the auxiliary verb (but past perfect uses "had"). The past perfect would be --> "I had never had to go to hospital."
Jonathan
LearnEnglish team