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Modals B – must/have to (Necessity – Deduction)

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In this series of lessons on modals we are dividing the meanings of modals into intrinsic and extrinsic meanings. In this lesson we are looking at the intrinsic and extrinsic meanings of ‘must’ and ‘have to/have got to’.

Look at these sentences:
My neighbours must control or discipline their children. They’re too noisy.
You’ve been working all week. You must be tired.

In the first sentence ‘must’ shows that the speaker sees this as a necessity. This meaning is intrinsic as it implies human control.

In the second sentence ‘must’ is used because the speaker is coming to a conclusion or deducing a situation. This meaning is extrinsic as the implication involves human judgement.

Must/ have to – Necessity

Must and have to are used to show that something is necessary:
The accommodation has to be booked well in advance.
The wine must be served chilled.

Must is used in more formal situations when stating rules:
Students must present their I.D. when borrowing books from the library.
Guests must refrain from smoking on the premises.

Have to/ have got to is more commonly used to describe a necessity which is not the speaker’s decision or in the speaker’s control:
We have to be there at least an hour before we are supposed to leave.
You’ve got to wear a tie to go in there.

‘Have got to’ is used in informal English although ‘have to’ is normally used with past simple in negatives and question forms. If ‘have’ is contracted then ‘have got to’ is used.
I had to go back to the restaurant for the umbrella I’d left there.
Where did you have to go?
He’s got to understand it’s not always about him.

‘Must’ has no past, perfect, continuous, infinitive or –ing and ‘have to’ is used. ‘Must’ is used for necessity in the future. ‘Have to’ is usually used for questions. ‘Must’ in question forms is seen as too formal or archaic.  Must is usually used for a necessity that is also a pleasure. I must go and see my sister. It’s her birthday tomorrow. = this is necessary but also a pleasure.

‘Mustn’t’ has a different meaning to ‘don’t have to’:
You must/have to wear a tie. = this is necessary
You don’t have to wear a tie. = this isn’t necessary but you can if you want to.
You mustn’t wear a tie. = this is necessary. Do not wear a tie.

Must/have to – deduction

Must is also used to deduce a situation about present and future events. Must + have + past participle is used for past events and their deduced result.
It must be very difficult to move to a new city where you don’t know anyone.
It must have been hard to get used to a different climate.
Jane isn’t at home. She must be doing the shopping.

Have to is used when the outcome is closer to what will happen.
There has to be a cheaper flight than this one. Keep looking.
They’ve got to make this easier to understand very soon.

Part 1 - Modals A – May/Might (Permission, Possibility)

Part 3 - Modals C – should/ought to (Obligation and Probability)

Lesson by Tristan, English teacher at EC Malta English school

Decide which verb is best for these:

  • 1) Visitors ___ refrain from using flash photography in the museum.






  • 2) You passed your exams. They ___ difficult.




  • 3) Do we ___ be there early?






  • 4) Patrons ___ wear a tie to be admitted to the restaurant.






  • 5) You ___ pick me up from the airport. I’ll get a taxi.






  • 6) I ___ be getting old. I can’t remember where I keep putting my car keys.






  • 7) John's not at work today. He ___ be unwell.






  • 8) Mary isn’t usually late. She ___ be stuck in traffic.






  • 9) You ___ got to be joking; travelling across Europe in your old car. You're asking for trouble.






  • 10) He ___ understand Italian to enjoy the opera. It’s the music that counts.