Материал: doichik_oia_modal_verbs_theory_and_practice

Will / would

Prediction

It will rain soon

Shall

Prediction (1st person)

Shall we find the way out?

Should / ought to

Obligation, Duty

You should do as you are told

Must

Total obligation

You must be quiet

Need / needn’t

Necessity / Absence

of

You needn‟t wait

necessity

can

Present

Can you hear the music?

could

Past

Could you drive when you were 18?

will be able to

Future

You will not be able to swim unless you

learn how to

have / had been able to

Perfect tense

I have been able to swim since I was 4

Verbs and verb phrases:

be (un)able to

She is unable to speak loudly

be (in)capable of

He is incapable of lying

manage to

They managed to persuade him

succeed in

You will succeed in driving

*Note

am/is/are able to would be unusual when

*Look! I can stand on my hands

we are commenting on something that is

happening at the time of speaking

**Note

Could, couldn’t or was/were (not) able to

**Jim could/couldn't run very fast

can describe natural and learned ability in

when he was a boy

the past, not related to any specific event.

Barbara could/couldn't sing very well

when she was younger

Jim was able to/was unable to run fast

But Could cannot be used when we are

when he was a boy

describing the successful completion of a

specific action. Here we use

was/were able to /

In the end they were able to rescue /

managed to

managed to rescue / succeeded in

succeeded in + V-ing

rescuing the cat on the roof.

If an action was not successfully

They tried for hours but they couldn't

completed, we may use couldn’t.

rescue the cat (also weren't able to /

didn’t manage to rescue the cat)

***Note

Could can be used when we are asking

***Could they rescue the cat on the

about a specific action (as opposed to

roof? (= did they manage to?)

describing it).

- No, they couldn’t It was too difficult

However, an affirmative response requires

an alternative to could

- Yes, they managed to (Not „could‟)

Can/could + Verbs of Perception

I can smell something burning (= I

Verbs of perception (see, hear, smell, etc)

smell something burning.)

are combined with can (or could with past

I can't see anyone (= I don't see

reference) to indicate that we can see, hear,

anyone.)

etc. something happening at the moment of

I listened carefully, but couldn’t hear

speaking.

anything (= I listened carefully, but

didn‟t hear anything)

Can/could + Verbs of mental ability

I can/can’t understand why he decided

(understand, imagine)

to retire at 50

Can’t/couldn’t cannot be replaced by the

I could/couldn’t understand why he

simple present or simple past when

had decided to retire at 50.

conveying the idea „beyond (my) control‟

I can’t (couldn’t) imagine what it

(impossible)

would be like to live in a hot

climate. (Not */ don‟t/I didn‟t imagine)

could have + V3 / would have been able

If it hadn't been for the freezing wind

to in conditional sentences and implied

and blinding snow, the rescue party

conditionals may be used to refer to ability

could have reached the injured man

or capacity that was not used because of

before nightfall

personal failure or lack of opportunity

I wish I could have helped you

*Note

The construction couldn’t have done

* They couldn’t have tried harder to

better means that the action was fulfilled

persuade him

in the best possible way

To say that things are generally

He can be very naughty

possible we use the modal verbs can

Drinks in restaurants can be very expensive

and may.

Antibiotics may lead to stomach disorders

May refers to formal contexts

Can has the meaning of „is sometimes‟

It can be quite cold in Cairo in January (=

or „is often‟ and refers to capability or

It is sometimes - or often - quite cold.)

possibility.

Could often refers to the past in this

It could be quite cold in Cairo in January

meaning

when I lived there (= It was sometimes - or

often - quite cold)

Could (or can) can also have a future

It can / could be quite cold when you get to

reference in this kind of context:

Cairo

* Note

If can is used for people, the effect is

* She can look quite attractive when she

often negative, even when the

wants to (= she doesn't usually look

adjective is positive.

attractive)

Can / can’t is used in sentences to

You can take the book when I finish reading

denote possibility / impossibility which

You can’t wait outside. It‟s raining.

depends on circumstances

He can’t talk with you now. He‟s busy

Can / can’t is used to denote

You cannot smoke in the café

possibility / impossibility according to

You cannot drive on the right side of the

the law or the rule

road in this country

Can / could is used in Wh-questions

Who can that be at this time of night?

and in indirect questions to ask about

What can be done?

possibility

Where could she be hurrying now?

I wonder where he can have left the key.

Present → Can / could + V1

Who could have broken the vase?

Past → Can / Could have + V3

Why can she have been so sad?

What else could have been done?

We use cannot / couldn’t to speak

You cannot get blood out of a stone

about impossible things

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