We can use have to + infinitive, must + infinitive and should + infinitive to express obligation (something you have to do).
Present
|
Positive
|
Negative
|
have to /
don't have to |
strong obligation (possibly from outside)
·
Children have to go to school.
|
no obligation
·
I don't have to work on Sundays.
You don't have to eat anything you don't like.
|
must / mustn't
|
strong obligation (possibly based on the speaker's opinion)
·
I must study today.
|
negative obligation
·
You mustn't smoke here.
|
should / shouldn't
|
mild obligation or advice
·
You should save some money.
|
mild negative obligation or advice
·
You shouldn't smoke so much.
|
Be careful about the difference between mustn't and don't
have to!
Mustn't means it's not allowed, or it's a bad idea:
Mustn't means it's not allowed, or it's a bad idea:
·
You mustn't eat so much chocolate, you'll be sick
Don't have to means you don't need to do something, but it's fine if you want to do it:
·
I don't have to get up early at the weekend (of course, if I want to get up
early, that's fine, but I can stay in bed if I want).
Past
|
Positive
|
Negative
|
had to / didn't have to
|
obligation in the past
·
I had to wear a school uniform when I was a child.
|
no obligation in the past
·
We didn't have to go to school on Saturdays.
|
must*
|
changes to 'had to'
|
was not to
|
should have + pp / shouldn't have + pp
|
a past action which didn't happen: the advice / regret is too late
·
You should have gone to bed earlier, now you have missed the train.
|
a past action which didn't happen: the advice / regret is too late
·
You shouldn't have taken that job, it was a bad idea.
|
* Remember 'must have done' is a modal verb of deduction or
speculation, not obligation in the past. For example: Julie must have left. Her
coat's not here.
Was not to: must changes to had to and mustn't becomes was not to for obligation in reported speech. E.g. you mustn't tell my mother: she said I was not to tell her mother.
Was not to: must changes to had to and mustn't becomes was not to for obligation in reported speech. E.g. you mustn't tell my mother: she said I was not to tell her mother.
CAN, MUST, SHOULD, OUGHT TO, HAD BETTER
The most common modal verbs for talking about permission and obligation are
can/ could, must and should/ ought to.
I couldn’t take any photos in the museum, so I bought some postcards.
Passengers on the bus mustn’t distract the driver.
We should/ought to drive home on the motorway – it’s much quicker.
We can use should have or ought to have + past participle to talk
about past events which did not happen and which we regret.
We should
have / ought to have driven home on the motorway – it would have been quicker.
Had better is stronger and more urgent than should/ought to and is often used to
give strong advice or a warning. It normally refers to the immediate future.
You’d better post the parcels today or they won’t get there in time.
The negative is had better not NOT hadn’t better.
HAVE TO/HAVE GOT TO
We also use have to express
obligation. It can be used in any tense.
All passengers will have to fill in a form before
landing.
You don’t
have to tip the waitress unless you think the service was especially good.
We can also use have got to to
express obligation, but it is normally used for specific occasions rather than
repeated or general obligation.
I’ve got to buy a birthday present for my brother.
NEED
We use need/don’t need + to +
infinitive to say something is necessary/ unnecessary. You can use these
forms for habitual, general, and specific necessity.
You usually need to check in at least two hours
before a flight leaves.
I don’t need to take a raincoat. It’s going to be hot today.
As a modal (NEED + infinitive without to), NEED tends to occur only in the negative and interrogative.
You need not wait.
Need we wait?
My brother-in-law and his family stayed with us at Christmas. Need I say more?
When we want to say that something is unnecessary on a specific occasion,
we can also use needn’t + infinitive
without to.
You needn’t lock the car. Nobody will steal in this village.
We use don’t need to (NOT needn’t) for habitual or general
necessity.
I don’t
need to wear glasses. My eyesight is still good (NOT I needn’t wear glasses)
A modal must be followed by a verb so we cannot use the modal verb pattern if followed by a noun: Do you need anything?
When something was not necessary, but you did it, we can use either needn’t + have + past participle or sometimes didn’t need to + infinitive.
When something was not necessary, but you did it, we can use either needn’t + have + past participle or sometimes didn’t need to + infinitive.
We needn’t
have booked / didn’t need to book a table. The restaurant is empty!
When something was not necessary so you did not do it, we must use didn’t need to.
We had plenty of petrol so we didn’t need to stop, which saved
time. NOT We had plenty of petrol
so we needn’t have stopped, which saved time.
I didn't need to spend very long on my homework last night- it was quite easy.
I didn't need to spend very long on my homework last night- it was quite easy.
DARE
As a modal (DARE + infinitive without to), DARE tends to occur only in the negative and interrogative.
They daren't ask for any more money.
I dare not go yet.
Dare we go yet?
Alternatively, we can also use DARE as a full verb followed by the infinitive with or without to:
He didn't dare (to) say what he thought.
I don't dare (to) go yet.
Do we dare (to) go?
BE ABLE TO, BE ALLOWED TO, BE PERMITTED TO, BE SUPPOSED TO
As a modal (DARE + infinitive without to), DARE tends to occur only in the negative and interrogative.
They daren't ask for any more money.
I dare not go yet.
Dare we go yet?
Alternatively, we can also use DARE as a full verb followed by the infinitive with or without to:
He didn't dare (to) say what he thought.
I don't dare (to) go yet.
Do we dare (to) go?
BE ABLE TO, BE ALLOWED TO, BE PERMITTED TO, BE SUPPOSED TO
We often use be able to or be allowed to + infinitive to talk
about what is possible or permitted instead of can, particularly when we want
to use a form which can does not have.
From tomorrow we won’t be able to park here.
You’re not allowed to smoke in the
classroom.
Be permitted to + infinitive is used in formal
situations, e.g. notices and announcements, to say what can / can’t be done
according to the law or to rules and regulations.
It is
not permitted to take mobiles into the exam room.
We do not use it
followed by allowed to + inf.
NOT It isn’t allowed to take
mobiles into the exam room.
We can also use be supposed to +
infinitive to say what people should or shouldn’t do, often because of
rules. There is often a suggestion that the rules are not necessarily obeyed.
Students are not supposed to stay out after 12.00, but everyone does.
We are
supposed to check in at 3.50. What’s the time now?
You aren’t supposed to park here - it’s a surgery entrance.
OTHER PHRASES WHICH CAN BE USED WITH
MODAL MEANING
Be allowed to, be permissible to; be forbidden to, be banned from; be/feel
compelled to, be compulsory; be forced to, be obligatory; have the courage to.
We weren’t allowed to contact the
teachers. (It wasn’t permissible to contact them.)
permissible /pəˈmɪsəbl/ acceptable according to the law or a particular set of rules. E.g. permissible levels of nitrates /ˈnaɪtreɪt/ in water. Permissible (for somebody) (to do something) It is not permissible for employers to discriminate on grounds of age.
ban somebody from something E.g. He was banned from the meeting.
ban somebody from doing something E.g. She's been banned from leaving Greece while the allegations are investigated.
compel: /kəmˈpel/ to force somebody to do something; to make something necessary.
Compel somebody to do something E.g. The law can compel fathers to make regular payments for their children. I feel compelled to write and tell you how much I enjoyed your book.
Compel something Last year ill health compelled his retirement.
compulsory: /kəmˈpʌlsəri/ E.g. It is compulsory for all motorcyclists to wear helmets. English is a compulsory subject at this level. Compulsory education/ schooling. Compulsory redundancies
They were forced to wear army uniform. (Army uniform was compulsory)
obligatory (for somebody) (to do something): /əˈblɪɡətri/ E.g. It is obligatory for all employees to wear protective clothing
courage: /ˈkʌrɪdʒ/
pluck up (the) courage (to do something): to make yourself do something even though you are afraid to do it. E.g. I finally plucked up the courage to ask her for a date.
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permissible /pəˈmɪsəbl/ acceptable according to the law or a particular set of rules. E.g. permissible levels of nitrates /ˈnaɪtreɪt/ in water. Permissible (for somebody) (to do something) It is not permissible for employers to discriminate on grounds of age.
ban somebody from something E.g. He was banned from the meeting.
ban somebody from doing something E.g. She's been banned from leaving Greece while the allegations are investigated.
compel: /kəmˈpel/ to force somebody to do something; to make something necessary.
Compel somebody to do something E.g. The law can compel fathers to make regular payments for their children. I feel compelled to write and tell you how much I enjoyed your book.
Compel something Last year ill health compelled his retirement.
compulsory: /kəmˈpʌlsəri/ E.g. It is compulsory for all motorcyclists to wear helmets. English is a compulsory subject at this level. Compulsory education/ schooling. Compulsory redundancies
They were forced to wear army uniform. (Army uniform was compulsory)
obligatory (for somebody) (to do something): /əˈblɪɡətri/ E.g. It is obligatory for all employees to wear protective clothing
courage: /ˈkʌrɪdʒ/
pluck up (the) courage (to do something): to make yourself do something even though you are afraid to do it. E.g. I finally plucked up the courage to ask her for a date.
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