Ampersand Lab

Foundation grammar · Lesson 31 · A2

must, mustn't, don't need to

Use must when something is necessary, had to for the past, mustn't when it is necessary not to do something, and don't need to when something is not necessary.

Start the lesson

17Steps · about 30 minutes

In this lesson

must + infinitiveA1 screen of questions
must: it is necessaryB4 screens of questions
mustn't: it is necessary not to do itC1 screen of questions
don't need to: it is not necessaryD2 screens of questions
Put it together+3 screens of mixed questions

Point A of 4

must + infinitive

Two friends walk past a new café. One says: Their cakes are amazing. You must try one.

The form is must + infinitive (must do, must see etc.):

Subject must Infinitive
I / we / you / they / he / she / it must do, stop, go, write etc.
  • You must try the cakes.
  • I must go now.
  • She must stop working so late.

Point A · Extra practice

Complete each sentence with must.

  1. It's late. I go home now.

  2. You see this film. It's brilliant.

  3. We remember to buy milk on the way home.

Point B of 4

must: it is necessary

must says that you see something as necessary.

must has no past form. For yesterday, last week and so on, use had to.

  • The car is filthy. I must wash it.
  • That book is brilliant. You must read it.
  • We must buy some bread today. There's none left.
  • We had to buy some bread yesterday. (not 'We must buy ... yesterday')
  • I had to get a taxi home last night. The last bus had gone. (not 'I must get')

Point B · Exercise 31.1 · part 1 of 2

Complete the sentences. Use must + one of these verbs.

Use these

bebuychargemeetphoneseevisit

  1. Example

    My phone is nearly dead. I must charge it.

    AnswerMy phone is nearly dead. I must charge it.

  2. My cousin Dan is very funny. You him.

  3. There's no milk left. I some on the way home.

  4. You the castle while you're in Conwy. It's beautiful.

  5. I my mum tonight. It's her birthday.

Point B · Exercise 31.1 · part 2 of 2

Complete the sentences. Use must + one of these verbs.

Use these

bebuychargemeetphoneseevisit

  1. The interview tomorrow is very important. I on time.

  2. That new comedy is brilliant. You it.

Point B · Exercise 31.2 · part 1 of 2

Put in I must or I had to.

  1. Example

    I had to get the bus to work yesterday. My car wouldn't start.

    AnswerI had to get the bus to work yesterday. My car wouldn't start.

  2. It's nearly midnight. go to bed.

  3. I don't usually cook, but last night make dinner for six people.

  4. remember to buy a card for Ellie. Her party is tomorrow.

  5. I flew to Belfast last week. The flight was late and wait four hours at the airport.

Point B · Exercise 31.2 · part 2 of 2

Put in I must or I had to.

  1. My alarm didn't go off this morning, so get dressed in two minutes.

  2. I didn't answer Kirsty's message yesterday. reply to her today.

Point C of 4

mustn't: it is necessary not to do it

mustn't is short for must not.

I mustn't do something means it is necessary not to do it, because doing it would be wrong.

A grandmother and a small boy are in a museum. The boy reaches out towards an old vase. She says: You mustn't touch it.

  • I must hurry. I mustn't miss the train.
  • I mustn't forget to ring the dentist. (= I must remember to ring the dentist)
  • You mustn't worry. Everything will be fine. (= don't worry)
  • You mustn't touch the vase. (= don't touch it)

Point C · Extra practice

Complete each sentence with mustn't.

  1. This is a library. You talk loudly.

  2. I forget my keys again.

  3. You park here. It's for ambulances.

Point D of 4

don't need to: it is not necessary

I don't need to do something means that it is not necessary to do it.

You can also say needn't (= need not). I needn't do it = I don't need to do it.

Compare don't need to and mustn't:

don't need to mustn't
You don't need to go. You can stay here if you want. You mustn't go. You must stay here.
  • I don't need to wash the car. It isn't very dirty.
  • You don't need to buy any bread. I got some this morning.
  • I needn't wash the car. (= I don't need to wash it)
  • You needn't buy any bread. (= you don't need to buy any)

Point D · Exercise 31.3 · part 1 of 2

Complete the sentences. Use mustn't or don't need to (needn't) + one of these verbs.

Use these

cookdropforgetrushwaitwear

  1. Example

    I've already made a pie for tonight. You don't need to cook anything.

    AnswerI've already made a pie for tonight. You don't need to cook anything.

  2. The film doesn't start until eight. We .

  3. This plate belonged to my great-grandmother. You it.

  4. Go home if you're tired. You for me. I'll get a taxi later.

  5. We to lock the back door tonight.

Point D · Exercise 31.3 · part 2 of 2

Complete the sentences. Use mustn't or don't need to (needn't) + one of these verbs.

Use these

cookdropforgetrushwaitwear

  1. It's only a barbecue in the garden. You a suit.

Put it together · Exercise 31.4

Find the sentences with the same meaning.

Use these

  1. We must leave the dog at home.
  2. We couldn't leave the dog at home.
  3. We can't leave the dog at home.
  4. We don't need to leave the dog at home.
  5. We can leave the dog at home.

  1. Example

    We can take the dog with us.

    d

    AnswerWe can take the dog with us. We don't need to leave the dog at home.

  2. We must take the dog with us.

  3. We mustn't take the dog with us.

  4. We don't need to take the dog with us.

  5. We had to take the dog with us.

Put it together · Exercise 31.5 · part 1 of 2

Put in must, had to, mustn't or don't need to.

  1. Example

    You don't need to come with me. You can wait in the car if you like.

    AnswerYou don't need to come with me. You can wait in the car if you like.

  2. Example

    This curry is amazing. You must try it.

    AnswerThis curry is amazing. You must try it.

  3. There's plenty of food in the freezer, so we go to the supermarket.

  4. The freezer was empty yesterday, so we go to the supermarket.

  5. I want to hear all about your trip. You tell me everything.

  6. You tell Gran about the broken window. I don't want her to know.

Put it together · Exercise 31.5 · part 2 of 2

Put in must, had to, mustn't or don't need to.

  1. I leave now, or I'll miss my train.

  2. "Why are you so tired?" "I get up at five this morning."

  3. We book a table. The café is never busy on Mondays.

Lesson 31 · Result

How you did

Next lesson: shouldBack to the course

–Right

Each point

A. must + infinitive–Not checkedB. must: it is necessary–Not checkedC. mustn't: it is necessary not to do it–Not checkedD. don't need to: it is not necessary–Not checkedPut it together–Not checked