We use the modal verbs like must, should and ought to or equivalents words like have to, has to and will have to to say that it is necessary to do something. These are called modal verbs of recommendation or moral obligation.
Modal Verbs Of Recommendation or Moral Obligation
We use must to express a strong obligation.
- I must go to bed earlier.
- They must do something about it.
Note: The verb must only exists in the simple present and present perfect forms.
Have to/ has to/ will have to
The modal verbs Have to/ has to and will have to Express a necessity or obligation in the past, present and future.
Have to and has to express obligations in English in four present tenses.
Simple Present Tense
Affirmative: Have to/ Has to
Negative: Does not have to/ Don’t have to
Interrogative: Do/ Does + Subject + have to
Present Continuous Tense
Affirmative: Is/Are/Am + having to
Negative: Is/Are/Am + not having to
Interrogative: Is/Are/Am + subject + having to
Present Perfect Tense
Affirmative: Has had to / have had to
Negative: Has not had to/ have not had to
Interrogative: Has/ Have + subject + had to
Present Perfect Continuous Tense
Affirmative: Has been/ have been + having to
Negative: Has not/ have not + been + having to
Interrogative: Has / have + subject + been having to
Note: You can conjugate had to the same for past tenses as we did for present tenses. And Will have to express future obligations in English and you can conjugate according to the tenses of future.
- You have to make an appointment to see him.
- She has failed her exam. She has to retake it.
- We don’t have to buy the ticket.
- She’s having to move because she can’t stand the noise.
- The manager isn’t here, he‘s had to go to Islamabad on urgent business.
- They have been having to work hard.
- I had to break the window ! I lost my key !
- She was having to take care of the baby.
- She will have to retake exam again.
- I will be having to take your class.
Difference Between must and have / has to
Must and have/ has to have the same meaning in positive sentences, but a different meaning in negative sentences.
In the negative must not is still a necessity or an obligation no to do something (a prohibition) whereas don’t have to removes the necessity or obligation.
- You must do your homework.
- You have to do your homework.
- They must not eat during class.chew gum or talk on the phone.
- It is Saturday i don’t have to work hard.
- You must not smoke in the house.
- You don’t have to go to the party.
- He doesn’t have to accept the job.
Recommendation or moral obligation – should and ought to
The verb should and ought to only exists in simple present and present perfect forms.
- You should stop smoking ( = You ought to stop smoking.)
- It’s raining hard, the children ought to come indoors.
- I didn’t know you were married ! You ought to have told me !
- If you’d wanted to succeed, you should have worked harder at school.
- This pullover’s got holes in it, I should get a new one.
- This pullover’s got holes in it, I ought to get a new one.
- That’s awful ! You really oughtn’t to have done that, you know !