Modal Auxiliaries

- the simple infinitive to express a modalized event at present:

I can/could drive a car, ride a motorbike and sail a boat.

He should visit his parents more often.

- the progressive infinitive (be + verb -ing) to show an action in progress at present:

She must be reading a book.

- the perfect infinitive (have + verb -en) to indicate reference to the past:

She could have phoned her friend but she didn’t.

- the perfect progressive infinitive (have + been + verb -ing) to suggest an activity in progress in the past:

She may have been reading a book when you phoned her.

- In passive sentences modal verbs combine with the simple passive infinitive (be + verb -en) to refer to an event in the present and with the perfect passive infinitive (have + been + verb -en) to indicate an event in the past:

active They could paint the house before they sell it.

passive The house could be painted before they sell it.

modal + be + verb -en

active They could have painted the house before they sold it.

passive The house could have been painted before they sold it. modal + have + been + verb -en

- In reported speech, could, would, might, should replace the corresponding can, will, may and shall:

‘I can come’, she said. direct speech

She said she could come. reported speech

The main modal verbs have corresponding modal paraphrases which can be used in all tenses: can – be able to, may - be permitted to, be allowed to, must – have to:

can I am/ was/ will be able to ski.

may Am/ was/ will I be permitted to come in?

must. You have to/ had to/will have to study.

Have to is the only modal paraphrase that forms the interrogative and the negative with the auxiliary do:

Do I have to finish the book by next month?

I don’t have to finish the book by next month.

Did I have to be in time for school?

I didn’t have to be in time for school.

The major semantic values of the modal verbs are given the following sections.

CAN/COULD

Can may be used :

1. To express a present or future physical or mental ability :

My sister can speak three foreign languages. Martin can help us tomorrow.

2. To express continuity with verbs of perception (to hear ; to see) :

I can hear that noise now.

Henry can see the plane now.

3. To express permission in informal English. Note the difference :

Can I borrow your umbrella ? (informal)

May I borrow your umbrella ? (formal)

4. To express possibility when certain circumstances permit :

If my cousins come to my village, we can swim. (There is a big river near the village.)

If my cousins come to my village, we may swim. (But we may also do other things, too : we may play in the fields, we may feed the animals, we may go to the forest, etc.)

5. To express impossibility or disbelief. In this case can may be followed by Present or Perfect Infinitive :

Can Jane make such a mistake?

It's only 7 o'clock ; they can't be at school now.

The boy can't have given a better answer than this one.

6. To express polite requests :

Can we call on you later?

Could may be used :

1. To express a past physical or mental ability :

When she was young, she could skate very well.

With this meaning of capability, can/could maybe replaced by to be able to :

We can/are able to understand him very well.

She knew the town well so she could/was able to advise us what to visit.

But, when the meaning is that of achievement, to manage to, to succeed in, to be able to and not can/could must be used :

I am sure that, if you are attentive, you are able to do such a difficult exercise. Although the driver was badly hurt, he was able to get out of the car before the engine exploded.

However, in the negative both could not and was/were not able to are possible : I don't know why William could not/was not able to finish that book. To express a Present Conditional :

You could get there in time if you took a taxi.

3. To express a polite request :

Could you show me the way to the railway station?

Such a request is more polite than the one with can.

4. To express past occurrences which are no longer possible today :

Before World War 11 such cars could often be seen in the streets.

5. To express a past possibility depending on certain circumstances :

At the seaside we could buy a lot of souvenirs. (There were a lot of shops near the beach.)

6. To express past permission :

As we had all our papers in order, we could pass through the customs very rapidly.

May – might

May can be used :

1. To express formal permission : May I open this window? Yes, you may.

No, you may not/must not.

With this meaning, may can be replaced by to be allowed to/to be permitted to : You may go to the cinema this week, you were allowed/permitted to go to the cinema last week, and you will be allowed/permitted to go there next week, too.

2. To express possibility :

You may know her.

It may rain in the afternoon.

In this case may can be replaced by it is possible/maybe/perhaps :

It is possible for you to know her.

Perhaps/Maybe you know her.

It is possible it will rain in the afternoon.

Perhaps/Maybe it will rain in the afternoon.

When may is followed by a Continuous Infinitive, it expresses possibility of something that continues now :

Mother may be sleeping now.

May followed by Perfect Infinitive expresses the possibility that an action took place in the past :

The little girl may have lost the key. (It is possible that she lost the key.)

3. To express prohibition (especially in official notices) :

Candidates may not bring dictionaries into the examination room.

4. To express doubt, uncertainty :

Who may that old man be? (archaic form)

5. To express wish, hope :

May all your dreams come true!

May good luck attend you!

6. In subordinate clauses of concession :

However difficult/No matter how difficult these exercises may be, you must do them all.

7. In direct object clauses following the verbs to hope, to trust, etc.

She hopes/trusts that you may find tickets for this performance.

8. In subordinate clauses of purpose:

Speak louder so that all of us may hear you.

Mention must be made of the fact that the examples 5, 7 and 8 are considered to be formal.

Might can be used :

1. To express permission connected with the past :

I understood then that he might go out of the room whenevey he wanted.

2. To express present/future/past possibility. This possibility is a little more remote than the possibility expressed by may :

Your cousin might be in the garden now. (present)

Granny might arrive on Thursday. (future)

The foreigner thought that he might find the way to the museum by himself. (past) Might followed by a Continuous Infinitive expresses the possibility of something to continue :

Your sister might still be sleeping.

When might is followed by Perfect Infinitive, it expresses a past possibility :

Our neighbours might have heard some noises when our car was stolen.

The construction made up of might and a Perfect Infinitive Continuous expresses a possible action which was continuing at a certain moment in the past :

The kids might have been watching a cartoon at that time.

3. To express a Present Conditional :

If you speak English, you might get that job.