Intermediate grammar · Unit 32 · B1

must mustn't needn't

Modals

Use must for what is necessary, mustn't for what you must not do, needn't or don't need to for what is unnecessary, and keep needn't have (done) (you did it, needlessly) apart from didn't need to (do) (it was unnecessary, whether or not you did it).

Go to the exercises

A must and mustn't

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

You mustn't do something = do not do it.

  • Please don't repeat what I told you. You must keep it to yourself.
  • The taxi is outside. We must get a move on.
  • You must keep it to yourself. You mustn't tell anybody. (= don't tell anybody)
  • The baby has just gone down. We must be quiet. We mustn't wake her.

B needn't and don't need to

You needn't do something = it is not necessary to do it, although you can if you want.

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

Note the form: don't need to do, but needn't do (without to).

needn't mustn't
You needn't tell Dad. I'll tell him myself. (= it is not necessary) You mustn't tell Dad. I don't want him to know. (= don't tell him)
  • The film doesn't start for an hour. We needn't rush. (= it is not necessary to rush)
  • Ava can stay at home. She needn't come to the tip with us.
  • We don't need to rush.

C needn't have (done)

Mo and Leanne booked a table for their anniversary. When they arrived on a wet Tuesday evening, they were the only customers in the restaurant.

They needn't have booked a table. They booked one, and now they know that it was not necessary.

needn't (do) needn't have (done)
It'll be fine. You needn't worry. It was fine. You needn't have worried.
It is not necessary. You worried, but it was not necessary.
  • We needn't have taken the umbrellas. It didn't rain once.
  • I needn't have cooked so much. Half the guests didn't turn up.

D needn't have (done) or didn't need to (do)?

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

He didn't need to do something = it was not necessary. The sentence does not say whether he did it or not; that is left to the context.

You can also say didn't have to with this second meaning.

  • Why did Tom set off at six? He needn't have left so early. He could have had a lie-in.
  • Tom didn't need to leave early, so he didn't.
  • Tom didn't need to leave early, but the roads are quieter at dawn, so he did.
  • Tom didn't have to leave early.

Exercises

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

  1. You mustn't get out.
  2. You mustn't panic.
  3. You mustn't tell anybody.
  4. You mustn't throw it away.
  5. You mustn't be late back.
  6. You mustn't shout.
  7. You mustn't move anything.

  1. You must keep your voice down.f

    You must keep your voice down. You mustn't shout.

  2. You must keep the receipt.

  3. You must stay calm.

  4. You must be home by eleven.

  5. You must leave the room exactly as it is.

  6. You must stay in the car.

  7. You must keep this between us.

32.2 Which is correct? Choose the right word from the brackets for each blank.

  1. The film doesn't start until eight. We needn't rush. (mustn't / needn't)

    The film doesn't start until eight. We needn't rush.

  2. I need to speak to the plumber. I remember to ring him. (must / mustn't)

  3. I need to speak to the plumber. I forget to ring him. (mustn't / needn't)

  4. Take your time with the menu. You choose straight away. (mustn't / don't need to)

  5. These are our passports. We lose them. (mustn't / needn't)

  6. You wait for me. Start eating and I'll catch you up. (mustn't / needn't)

  7. The ice on the pond is very thin. We do anything silly. (mustn't / needn't)

  8. I know exactly what happened. You explain. (mustn't / don't need to)

  9. A: What sort of car are you after? Something new? B: It be new. That doesn't bother me. It have a big boot, though, for the dogs. (mustn't / needn't) (must / mustn't)

32.3 Complete the sentences. Use needn't + one of these verbs.

comekeepleavewalkworry

  1. The match doesn't kick off for another hour. We needn't leave the house yet.

    The match doesn't kick off for another hour. We needn't leave the house yet.

  2. I can take the dog to the vet on my own. You with me.

  3. We back from the pub. Dad says he'll pick us up.

  4. Throw those old bank statements away. You them.

  5. I'll text you as soon as I land. 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. (For could have, see Unit 27.)

  1. Why did you run for the bus? Why didn't you wait for the next one?

    You needn't have run for the bus. You could have waited for the next one.

    You needn't have run for the bus. You could have waited for the next one.

  2. Why did you buy a new kettle? Why didn't you borrow ours?

  3. Why did they get a taxi from the station? Why didn't they ring us for a lift?

  4. Why did he text me at midnight? Why didn't he wait until the morning?

  5. Why did you snap at me? Why weren't you more patient?

32.5 Are these sentences correct? Change them where necessary. Where the sentence is correct, write OK.

  1. The shop's open late tonight. We don't need hurry.

    The shop's open late tonight. We don't need to hurry.

    The shop's open late tonight. We don't need to hurry.

  2. This is between you and me. You mustn't tell anybody.

    OK

    This is between you and me. You mustn't tell anybody.

  3. You needn't to whisper. There's nobody else in the house.

  4. I needn't have gone into work, so I stayed at home.

  5. This bus goes straight to the airport. You don't need to change.

  6. You mustn't wear a tie. It's fine to come in jeans.

  7. I needn't have paid, so I put my purse away.

  8. I needn't have bought so much bread. Half of it went stale.

See also