A Forming senteces with modals

B Modals of permission

1 Can, could and may are used to talk about permission

• can

  Can I go out? Is that all right? (asking for permission)

  He can go to the cinema on his own. That's OK. (giving permission)

• could

  Could I borrow some money? (asking for permission / more polite than Can I...?)

  She said that I could go to the party, (reporting permission)

• may

  May I leave class early today? I've got a job interview. (asking for permission - for more formal situations)

2 Other non-modal verbs and expressions can be used to talk about permission (let, allow, permit)

• let + object + infinitive

  My parents let me go to concerts with my friends.

  Note: let does not have a passive form.

• allow (to)

  They allow her to watch TV. (allow + object + to-infinitive)

  I was allowed to leave class early today, (passive + to-infinitive)

  Note: in a sentence like this, where the permission resulted in an action, we can't use could (NOT CORRECT: I could leave the class early today).

• permit (to)

  You are permitted to smoke only in the designated areas.

  Smoking is permitted only in the designated areas, (rules made by someone else - more formal than allow)

C Modals of prohibition

1 Can't, couldn't, mustn't and may not are used to talk about prohibition:

• can´t

  He can't go to a nightclub. He's too young, (prohibition)

• couldn't (past form of can)

  He said I couldn't use it. (he refused permission)

• mustn't

  You mustn't talk in the library. Please be quiet! (direct order)

  Note: the past form of this sentence is: Talking wasn't allowed in the library.

• may not

  may not leave the room during the exam. (prohibition)

2 Other non-modal expressions can be used to talk about prohibition and rules that are made by someone else (not supposed to, not allowed to, not permitted to, forbidden/ban):

• not supposed (to)

  You're not supposed to park here.

• allow (to)

  My manager won't allow me to take the day off.

  You're not allowed to take photographs here.

• permit (to)

  You are not permitted to smoke in here.

  Smoking is not permitted here, (more formal than allow)

• forbid/ban

  Cars are forbidden/banned/prohibited in the town centre.

D Modals of obligation and necessity

1 We use must/mustn't to express strong obligation or necessity:

• must (stronger than should/had better):

  I must post the letter straightaway. (I, personally, feel it is necessary)

  Note: For the future of must we use will/'ll have to and for the past we use had to:

  I'll have to hurry or I'll miss the last bus.

  She had to go home because she felt ill.

  Where emphasis is needed, such as in legal documents, shall is used.

  The tenant shall pay the rent on the first day of each calendar month.

• mustn't (stronger than shouldn't):

  You mustn't forget your keys, (an obligation NOT to do something)

2 Other non-modal verbs can be used to talk about strong obligation and necessity(have to, make):

• have (got) to is used when the situation or someone else (not the speaker) makes it necessary:

  I have to work late tonight. My boss says so.

  We'll have to invite my mother next time, (the situation makes it necessary)

  I had to go to the doctor's yesterday, (past time - it was necessary)

• make is used for a strong obligation imposed by someone else:

  Her parents make her wash the dishes, (make + object +infinitive)

  She is made to wash the dishes, (passive + to-infinitive)

3 Should/shouldn't, ought to/ought not to are used to express a slightly less strong obligation or a duty/responsibility:

You should/ought to phone and let them know you'll be late. (decency / an expectation)

They shouldn't leave without permission.

You ought to call your mother on her birthday.

4 Should have is used when something was advisable to do, but you didn't do it:

You should have had an early night last night. You look tired, (you didn't go to bed early)

You ought to have let them know you’d be late.

5 Supposed to is a non-modal expression we use to talk about our responsibilities and the correct way of doing things:

What time are we supposed to be at the office?

E Modals of lack of obligation and necessity

We use do not have to/do not need to/needn´t, needn't have/didn't need to to express lack of obligation or necessity:

You don't have to wash those dishes. They're clean. (It's not necessary)

I didn't have to go to the doctor's yesterday. (It wasn't necessary)

needn't/don't need to

You needn't/do not need to wash those dishes. They're clean. (It's not necessary)

Note: need can be a modal verb (negative = needn't) or an ordinary verb (negative = don't need).

F Modals of advice and recommendation

1 Should(n´t)/should have, ought to/ought to have are used to give advice and recommendations. (Ought to is less commonly used than should.)

You should see it - it's a great film, (recommendation)

You shouldn't/ought not to go to work today - you really don't look well, (advice)

You should have told me you weren't coming. I waited for ages.

He shouldn't have shouted at me.

2 The non-modal expression had better (not) is stronger than should/shouldn't.

It's cold. You'd better wear a coat, (it's the best thing to do)

Hurry up! We'd better not be late.

G Modals of deduction and speculation

Modal verbs like must, can't, may, might and could can be used to express degrees of certainty about events in the past.

Very certain

When you are very certain that something has happened, use must.

James must have attended the seminar. (His name was on the attendance sheet.)

Less certain

When you are less certain, use may, might or could.

James may have attended the seminar. (It's possible but there isn't strong evidence)

James might have attended the seminar.

James could have attended the seminar.

Impossible

When it's impossible that something has happened, use can't.

James can't have attended the seminar. (He did not go to school that day.)

Mistakes in the past

When you want to talk about something you regret doing in the past, use should.

I shouldn't have left my wallet on the desk. (Someone stole it and I'm unhappy. It was a mistake to leave it on the desk.)

Form

We use the modal verb + have + past participle

You shouldn't have spent so much money.

It must have rained last night. The ground is wet.

I can't have lost my phone. I remember putting it in my bag.

Exercises