Expressing possibility Logical assumptions

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Modal verbs

Autor: Mgr. Jana BálkováDatum: 23. 9. 2012

• What do verbs may, might, could express?• What time do they refer to?

After could, may, might we can use simple or continuous form, passive form

• The story could be true, I suppose.• Sarah may be working late tonight.• The question may be answered later at the meeting.

Rachel: “Whose bag is that?”Donna: “I don’t know. It may belong to Tom’s friend.”Tracy: “It might be a bomb. It could explode at any moment.”

Must vs. can’t

We use……………when we realize that something is certainly true.

We use ……………when we realize that something is impossible.

Examples – complete must or can’t

1) She isn’t answering the phone. She …………be out.

2) Life ……….be easy when you have to spend it in a wheelchair.

3) Nick ……..be touring Scotland. I saw him here this morning.

4) Andrew isn’t here. He……..still be working.

5) We haven’t walked far. You………..be tired yet.

6) I had my keys a moment ago. They…….. Be here somewhere.

Vicky, Emma and Mat are at a club in town.Vicky: Where’s Daniel? He should have been here.Emma: He may have got lost. It’s not easy to find this place.Mat: He could have forgotten all about it, I suppose.

• these modal verbs are used with the perfect form (have+past participle)

• What do verbs should have…, may have…, could have… express?

• What time do they refer to?

Other examples:

My watch says it’s only 10 past two. It must have stopped.You can’t have been studying properly because you’ve failed the test.Where are my keys? They may have been left at home.

Obligation – necessity - prohibition

MUST – strong obligation coming from a speakerI really must eat something.

HAVE TO – obligation coming from outside (laws, regulations,…)Children have to wear uniforms to school in Britain.

OUGHT TO – something is the right thing to do but we don’t always do it (= should)

We ought to behave in an environmentally-friendly way.

Which modal verb can express obligation, necessity or prohibition?

Complete the sentences with HAVE TO, MUST, OUGHT TO.

1. I ……………… go to the airport. I’m meeting someone.

2. The doctor tells me I ……………….exercise.

3. I’ve gained some weight. I …………………… exercise.

4. I think I won’t go out. I ………………… study tonight.

5. David’s leg is broken. He…………………… go to hospital.

6. I ……………… buy a newspaper. I want to see the racing results.

7. We ……………… invite Tim and Laura, they invited us last time.

8. We ………… invite Tim and Laura, they’re wonderful company.

9. If you don’t feel well, you………………take an aspirin.

10. Daniel ……………… go to the bank. He has no money.

11. Emma …………… go to the dentist yesterday.

Expressing necessity/ lack of necessityMUST / HAVE TO / NEED – to express necessity

We have to hurry or we’ll miss the plane.The lawn needs cutting.

DON’T NEED TO / DON’T HAVE TO / NEEDN’T – to express lack of necessity (present)She doesn’t need to work, her husband is well-off.You needn’t tell Jill, I’ve already phoned her.

DIDN’T NEED TO / DIDN’T HAVE TO – to express lack of necessity (past)

She didn’t need to cook as they went out for dinner.They didn’t have to call an ambulance, nobody was injured.

Expressing prohibition

MUSTN’T – to express prohibitionYou mustn’t come late to school.Donna mustn’t stay out late at night.

NEEDN’T – to express lack of obligationYou needn’t wash the car. You brother’s done that.

CAN’T / MAY NOT – to express prohibition (= be not allowed)Students can’t smoke at school.Students may not cheat during the test. (more formal)

DIDN’T NEED TO vs. NEEDN’T HAVE -EDDIDN’T NEED TO = sth. wasn’t necessary

• Mark didn’t need to hurry. He had lots of time. He drove slowly along the motorway.

• We didn’t need to go to the supermarket because we had plenty of food. (=we didn’t go)

NEEDN’T HAVE +past participle = sth. wasn’t necessary but happened

• Mark needn’t have hurried. After driving at top speed, he arrived half an hour early.

• We needn’t have gone to the supermarket, we already had a pizza. (= but we went there)

Finish the sentences using didn’t need to or needn’t have –ed:

1. The previous owners had already decorated the flat so we…………………………………………….(decorate / it / ourselves.)

2. Luckily we were able to sell our old flat before we bought the new one we………………………………(borrow / any money.)

3. It was very hot yesterday so I watered all the flowers. And now it’s pouring with rain. I………………………(bother)

4. We’ve done the journey much more quickly than I expected. We……………………………(leave / so early)

5. A friend had already given me a free ticket to the exhibition, so I ……………………(pay / to go in)

6. Service was included in the bill, so we …………………………… (leave / a tip) was a waste of money.

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