Modal
verbs of obligation
Modal
verbs part 2 - obligation :
must,
have to, should and ought
to
There are two types of modal
verbs of obligation ;
- those that primarily express a firm obligation or necessity - must and have to
- those that express a recommendation or moral obligation - should and ought to
Firm obligation, etc. - must and have to
The verb must only exists in the simple present and present perfect forms.While the present form can express obligation, necessity, certainty or strong probability, the present perfect forms only express a strongly felt opinion or supposition.
| All persons | Present | Present perfect |
| Affirmative | must |
must have |
| Negative | must not, mustn't | must not have, mustn't have |
If other tenses are required, the speaker or writer must use forms of the synonymous modal verb "have to" . This modal auxiliary has all normal tenses, including progressive or continuous forms; these are not common, but need to be used in some cases.
| Principal tenses | Present | Present perfect | Past | Future |
| Affirmative: | has
to, have to |
has
had to have had to |
had
to |
will have to |
| Negative; |
does
not have to, do not have to , doesn't have to don't have to |
has
not had to have not had to |
did
not have to didn't have to * |
will
not have
to won't have to |
| Progressive or continuous | am
having to is having to, are having to |
has
been having
to have been having to |
was
having to were having to |
will be having to |
* The form
"had not to"
is sometimes used, but it is generally
considered to be archaic.
For example an alternative to I have to is I've got to.
For more on this, see Get and got
Got to :
In spoken English, and in the present form only, have to is often substantiated by the word got;For example an alternative to I have to is I've got to.
For more on this, see Get and got
Examples of must and have to being used to express :
a. Firm obligation or necessity
b. Certainty or strong probability.
c. Must have only : supposition
a1)
You
must see a doctor at once !
a2) I have to be at school tomorrow at 8 a.m. I have an exam !
a21) I've got to be at school tomorrow at .....
a3) You mustn't touch that plate, it's too hot.
a4) I had to see a doctor, because I felt very sick.
a5) I had to break the window ! I lost my key !
a6) The manager isn't here, he's had to go to Paris on urgent business.
a7) Tomorrow the President will have to open Parliament.
a8) She's having to move because she can't stand the noise.
a9) I'm having to take out this detonator very slowly, to avoid an explosion.
a10) Oh you're so kind! You didn't have to do it as well as that !
b1) He must be over eighty, he was born in 1930.
b2) If my brother's not in London, he has to be in New York.
b3) I've got all the right answers, I must be one of the winners !
b4) If I remember correctly, it has to be here.
c1) I can't find my laptop, I must have left it in the train.
c2) If they're out, they mustn't have heard the news.
Attention
! a2) I have to be at school tomorrow at 8 a.m. I have an exam !
a21) I've got to be at school tomorrow at .....
a3) You mustn't touch that plate, it's too hot.
a4) I had to see a doctor, because I felt very sick.
a5) I had to break the window ! I lost my key !
a6) The manager isn't here, he's had to go to Paris on urgent business.
a7) Tomorrow the President will have to open Parliament.
a8) She's having to move because she can't stand the noise.
a9) I'm having to take out this detonator very slowly, to avoid an explosion.
a10) Oh you're so kind! You didn't have to do it as well as that !
b1) He must be over eighty, he was born in 1930.
b2) If my brother's not in London, he has to be in New York.
b3) I've got all the right answers, I must be one of the winners !
b4) If I remember correctly, it has to be here.
c1) I can't find my laptop, I must have left it in the train.
c2) If they're out, they mustn't have heard the news.
Take care to distinguish correctly between "had to" and "must have"
They had to go to
London
= They were obliged to go to London
They must have gone to London.
= In my opinion, they have certainly gone to London.
► Other uses of the verb have:
see the verb to have.= They were obliged to go to London
They must have gone to London.
= In my opinion, they have certainly gone to London.
Recommendation or moral obligation - should and ought to
The verb should only exists in the simple present, and present perfect formsForms of should
| All persons | Present | Present perfect |
| Affirmative | should |
should have |
| Negatve | should not, shouldn't | should not have, shouldn't have |
The verb ought to only exists in simple present and present perfect forms
Forms of ought to
| All persons | Present | Present perfect |
| Affirmative | ought to |
ought to have |
| Negative | ought not to, oughtn't to | ought not to have, oughtn't to have |
Should and ought to are more or less synonymous
Examples:
a1) You should stop smoking ( = You ought to stop smoking.)
a2) It's raining hard, the children ought to come indoors.
a3) I didn't know you were married ! You ought to have told me !
a4) If you'd wanted to succeed, you should have worked harder at school.
a5) This pullover's got holes in it, I should get a new one.
a6) This pullover's got holes in it, I ought to get a new one.
a7) That's awful ! You really oughtn't to have done that, you know !
a1) You should stop smoking ( = You ought to stop smoking.)
a2) It's raining hard, the children ought to come indoors.
a3) I didn't know you were married ! You ought to have told me !
a4) If you'd wanted to succeed, you should have worked harder at school.
a5) This pullover's got holes in it, I should get a new one.
a6) This pullover's got holes in it, I ought to get a new one.
a7) That's awful ! You really oughtn't to have done that, you know !
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