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Unit 32 · Modals

must mustn't needn't

Study

A

You must do something = it is necessary that you do it:

›

Don't tell anybody what I said. You must keep it a secret.

›

We don't have much time. We must hurry.

You mustn't do something = don't do it:

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You must keep it a secret. You mustn't tell anyone. (= don't tell anyone)

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We must be very quiet. We mustn't make any noise.

B

You needn't do something = it's not necessary to do it (but you can if you want):

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We have plenty of time. We needn't hurry. (= it is not necessary to hurry)

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Joe can stay here. He needn't come with us. (= it is not necessary for him to come)

You can also use don't/doesn't need to:

›

We don't need to hurry.

Note that we say 'don't need to do', but 'needn't do' (without to).

Compare needn't and mustn't:

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You needn't tell Steve. I can tell him myself. (= it is not necessary)

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You mustn't tell Steve. I don't want him to know. (= don't tell him)

C

Study this example situation:

Paul and Sarah reserved a table at a restaurant. But when they went to the restaurant, it was almost empty.

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They needn't have reserved a table.

This means: they reserved a table, but now they know this was not necessary.

D

He needn't have done something = he did it, but now we know that it was not necessary:

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Why did he get up at 5 o'clock? He needn't have got up so early. He could have stayed in bed longer.

He didn't need to do something = it was not necessary to do it. It doesn't matter whether he did it or not:

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He didn't need to get up early, so he didn't.

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He didn't need to get up early, but it was a beautiful morning, so he did.

You can also say 'He didn't have to get up' in these examples.

Compare needn't (do) and needn't have (done):

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Everything will be OK. You needn't worry. (it is not necessary)

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Everything was OK. You needn't have worried. (you worried, but it was not necessary)

must ('You must be tired') → Unit 28 have to and must → Unit 31 Modal verbs (can/could/will/would etc.) → Appendix 4 American English → Appendix 7

Exercises (5)

0/5 exercises checked
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32.1

Which goes with which? Find the sentences with a similar meaning.

  1. 1You must be very quiet.
  2. 2You must remember your password.
  3. 3You must be brave.
  4. 4You must be on time.
  5. 5You must leave the furniture as it is.
  6. 6You must go away.
  7. 7You must forget what happened.
  1. aYou mustn't stay here.
  2. bYou mustn't be afraid.
  3. cYou mustn't think about it.
  4. dYou mustn't forget it.
  5. eYou mustn't be late.
  6. fYou mustn't make any noise.
  7. gYou mustn't move anything.
32.2

Which is correct?

  1. 1
    We have plenty of time. We mustn't / needn't hurry. (needn't is correct) example
  2. 2
    I have to talk to Gary. I must / mustn't remember to call him.
  3. 3
    I have to talk to Gary. I mustn't / needn't forget to call him.
  4. 4
    There's plenty of time for you to decide. You mustn't / don't need to decide now.
  5. 5
    These are important documents. We mustn't / needn't lose them.
  6. 6
    You mustn't / needn't wait for me. You go on and I'll join you later.
  7. 7
    This is a dangerous situation and we need to be careful. We mustn't / needn't do anything stupid.
  8. 8
    I understand the situation perfectly. You mustn't / don't need to explain further.
  9. 9
    a: What sort of house do you want to buy? Something big? b: It mustn't / needn't be big – that's not so important. But it must / mustn't have a nice garden.
32.3

Complete the sentences. Use needn't + verb. Choose from:

comekeepleavewalkworry
  1. 1
    We have plenty of time. We needn't yet.example
  2. 2
    I can manage the shopping alone. You with me.
  3. 3
    We all the way home. We can get a taxi.
  4. 4
    You can delete these emails. You them.
  5. 5
    I'll be all right. You about me.
32.4

Write two sentences for each situation. Use needn't have in the first sentence and could have in the second (as in the example). For could have, see Unit 27.

  1. 1
    Why did you rush? Why didn't you take your time?
    You needn't have . You could have your time.example
  2. 2
    Why did you walk home? Why didn't you take a taxi?
    You needn't have home. You could have a taxi.
  3. 3
    Why did they stay at a hotel? Why didn't they stay with us?
    They needn't have at a hotel. They could have with us.
  4. 4
    Why did she phone me at 3 am? Why didn't she wait until the morning?
    She needn't have me at 3 am. She could have until the morning.
  5. 5
    Why did you shout at me? Why weren't you more patient?
    You needn't have at me. You could have more patient.
32.5

Are these sentences OK? Change them where necessary.

  1. 1
    We have plenty of time. We don't need hurry. example
  2. 2
    Keep it a secret. You mustn't tell anybody. example
  3. 3
    You needn't to shout. I can hear you perfectly.
  4. 4
    I needn't have gone out, so I stayed at home.
  5. 5
    This train is direct. You don't need to change.
  6. 6
    You mustn't lock the door. It's OK to leave it unlocked.
  7. 7
    I needn't have said anything, so I kept quiet.
  8. 8
    I needn't have said anything. I should have kept quiet.