Can and Could: Forms and Uses

1.

CAN
COULD
nstu.ru
Foreign Language (BA
in Linguistics, 45.03.02):
Practical Grammar,
Semester 3

2.

FORMS AND USE
• CAN is the present tense form, COULD is the past tense form
• COULD is used in two distinct ways:
1. In past-time contexts as a form of the Indicative Mood
2. In present-time contexts to express:
o unreality
o a more polite form
o more uncertainty than can

3.

COULD in past-time context
He could speak English when he was a child.
COULD in present-time context - unreality
He could speak English if necessary.
COULD in present-time context – more polite form
Could I help you?
COULD in present-time context – more uncertainty
Could it be true?

4.

MEANINGS OF
CAN / COULD
ABILITY
AND
CAPABILITY
POSSIBILITY DUE
TO
CIRCUMSTANCES
PERMISSION
UNCERTAINTY
AND DOUBT
IMPROBABILITY

5.

ABILITY AND CAPABILITY

6.

ABILITY AND CAPABILITY
I can imagine how angry he is.
He can read a little French.
• occurs in all kinds of sentences: affirmative, negative, interrogative
• is followed by the simple infinitive
• reference is made to the present, may also refer to the future (context)

7.

ABILITY AND CAPABILITY
• be able to also expresses the meaning of ability and capability
• if the time reference is not clear from the context or if it is necessary
to stress that the action refers to the future, will be able is used
• if actions refer to the past, could is used with simple infinitive, but
there have to be indications of past time in the sentence or in the
context, otherwise the meaning of could is different

8.

ABILITY AND CAPABILITY
• if there is no indication of past time in the context but the speaker
wishes to refer the action to the past, was/were able is used to avoid
ambiguity
• could with the perfect infinitive indicates that the action was not
carried out in the past
She could have explained the mystery.
Она могла бы объяснить эту тайну. (но не объяснила)

9.

CAN - future
We can discuss your paper after lunch.
WILL BE ABLE TO
He will be able to write to us from Portugal
COULD - past
Could the boy read before he went to school?
WAS/WERE BE ABLE TO
She was able to explain the mystery.

10.

POSSIBILITY DUE TO
CIRCUMSTANCES

11.

POSSIBILITY DUE TO CIRCUMSTANCES
You can see the forest through the other window.
• occurs in all kinds of sentences: affirmative, negative, interrogative
• is followed by the simple infinitive
• reference is made to the present, may also refer to the future

12.

POSSIBILITY DUE TO CIRCUMSTANCES
• if actions refer to the past, could is used with simple infinitive, but it
denotes only the ability or possibility of performing an action but
not the realization of the action
• a realized or an unrealized action is expressed with to manage or
to succeed
• an unrealized action in the past it also expressed with to fail

13.

POSSIBILITY DUE TO CIRCUMSTANCES
• to be able can also express the realization of that action depending
on the lexical character of the infinitive or the context
• could with the perfect infinitive indicates that the action was not
carried out in the past

14.

COULD in the past-time context
You could see the forest through the other window before the new block of
houses was erected.
Realized actions – TO MANAGE / TO SUCCEED
He managed to settle the difficulty.
He succeeded in attaining his aim.
Unrealized actions – TO FAIL
He failed to reach the peak

15.

BE ABLE TO: contrast
He was able to speak English well. (мог/умел)
Не was able to get the book from the library. (смог)
COULD with perfect infinitive
He managed to settle the difficulty.
He succeeded in attaining his aim.

16.

PERMISSION

17.

PERMISSION
You can take my umbrella.
• occurs in all kinds of sentences: affirmative, interrogative for requests
and negative for prohibitions
• is followed by the simple infinitive
• could is used in interrogative sentences for polite requests and also
in reported speech in accordance with the rule of sequence of tenses

18.

CAN’T for prohibition
You can't use my car today.
CAN for requests
Can I use your car?
COULD for polite requests
Could I use your car?
COULD in reported speech
He asked me if he could use my car

19.

UNCERTAINTY AND DOUBT

20.

UNCERTAINTY AND DOUBT
Can it be true? (Неужели это правда?)
• occurs only in interrogative sentences (in general questions)
• sentences of this kind are often emotionally coloured
• is followed by the different forms of the infinitive, depending on the
time reference

21.

UNCERTAITY AND DOUBT
• reference is made to the present, the verb is stative → simple
infinitive
• reference is made to the present, the verb is dynamic → continuous
infinitive
• reference is made to the past, the verb is stative → perfect infinitive
• reference is made to the past, the verb is dynamic → perfect
continuous infinitive

22.

CAN with simple infinitive for uncertainty and doubt
Can he really be ill?
Can it be so late?
CAN with continuous infinitive for uncertainty and doubt
Can she be telling lies?
Can he be making the investigation all alone?
CAN with perfect infinitive for uncertainty and doubt
Can he have said it?
Can she really have been at home all this time?
CAN with perfect continuous infinitive for uncertainty and doubt
Can she have been waiting for us so long?

23.

UNCERTAITY AND DOUBT
• could with reference to the present is also used in this way, implying
more uncertainty
Could it be true?
Could she be telling lies?
Could he have said it?
Could she have been waiting for us so long?

24.

IMPROBABILITY

25.

UNCERTAINTY AND DOUBT
It can't be true. (Не может быть, что это так. Вряд ли это так.)
• occurs only in negative sentences (emotionally coloured)
• is followed by the different forms of the infinitive, depending on the
time reference

26.

UNCERTAITY AND DOUBT
• reference is made to the present, the verb is stative → simple
infinitive
• reference is made to the present, the verb is dynamic → continuous
infinitive
• reference is made to the past, the verb is stative → perfect infinitive
• reference is made to the past, the verb is dynamic → perfect
continuous infinitive

27.

CAN with simple infinitive for improbability
He can’t be serious.
She can’t be responsible for this.
CAN with continuous infinitive for improbability
He can’t be sleeping at this hour.
They can’t be having dinner already.
CAN with perfect infinitive for improbability
He can’t have forgotten my name.
She can’t have left so early.
CAN with perfect continuous infinitive for improbability
He can’t have been sleeping all day.
They can’t have been working all night.

28.

UNCERTAITY AND DOUBT
• could with reference to the present is also used in this way making the
statement less categorical
It couldn't be true.
She couldn't be telling lies.
He couldn't have said it.
She couldn't have been staying at home all this time

29.

SPECIAL QUESTIONS
• can and could followed by different forms of the infinitive in special
questions are used for emotional colouring –to express puzzlement,
impatience, etc.
What can (could) he mean? (Что, собственно, он имеет в виду?)
What can (could) he be doing?
Where can (could) he have gone to?
What can (could) he have been doing all day?

30.

CAN AND COULD OPPOSITION
• could referring to the present is sometimes clearly opposed to can in
the following meanings:
1. ability
He can speak English.
He could speak English if necessary.
2. possibility due to circumstances
You can get the book from the library. You could get the book from the
library if necessary.
• could expresses unreality whereas can expresses reality

31.

CAN AND COULD OPPOSITION
• in other uses this difference between can and could disappears
1. permission
Can I use your pen?
Could I use your pen
2. uncertainty, doubt, improbability
Can it be true?
Could it be true?
It can't be true.
It couldn't be true
• could is used either as a milder or more polite form of can or as a
form implying more uncertainty than can

32.

ADVERBIAL CLAUSE OF PURPOSE
• can and could also occur in adverbial clauses of purpose
• it is, then, structurally dependent
I'll leave the newspaper on the table so that he can see it at once.
I left the newspaper on the table so that he could see it at once.

33.

SET PHRASES
• can’t help (doing) = не могу удержаться от… не могу не (делать)
She can't help crying.
He couldn't help laughing
• can’t but (do) = ничего другого не остается, как...
I can't but ask him about it.
They couldn't but refuse him
• can't possibly (do) = просто не могу/может/могут (сделать)…
Не can't possibly do it.
I couldn't possibly refuse him

34.

SUMMARY

35.

CAN AND COULD: MAIN MEANINGS
Can:
• ability / capability — She can swim.
• possibility due to circumstances —
You can see the house from here.
Could:
• past ability / possibility — She could
swim when she was five.
• unreal present / future — She could
help us if necessary.
• permission — You can use my car.
• uncertainty / doubt (interrogative) —
Can it be true?
• more polite request — Could I use
your phone?
• greater uncertainty — Could it be true?
• improbability (negative) — It can’t be
true.
• less categorical improbability — It
couldn’t be true.

36.

TYPES OF INFINITIVE FOR UNCERTAINTY, DOUBT
AND IMPROBABILITY
reference is made to the present, the verb is stative → simple infinitive
reference is made to the present, the verb is dynamic → continuous
infinitive
reference is made to the past, the verb is stative → perfect infinitive
reference is made to the past, the verb is dynamic → perfect continuous
infinitive

37.

SELF-CHECK

38.

QUESTIONS
1.
What is the main difference between can and could in terms of time reference?
2.
When can could refer to the present or future?
3.
How does could make a request different from can?
4.
How does could differ from can when expressing uncertainty?
5.
How is a specific successful action in the past expressed?
6.
What does could + perfect infinitive express?
7.
What does can’t express in He can’t be serious?
8.
What is the difference between can’t and couldn’t in expressing improbability?
9.
When is the continuous infinitive used with can/could?
10. When is the perfect infinitive used with can/could?

39.

ANSWERS
1. Can refers to the present/future; could can refer to the past or express an unreal
present/future.
2. Could refers to an unreal present or future possibility.
3. Could is a more polite form of can.
4. Could expresses greater uncertainty than can.
5. A specific successful past action is expressed with was/were able to or managed to.
6. Could + perfect infinitive expresses a past possibility that was not realized.
7. Can’t expresses improbability.
8. Couldn’t expresses improbability less categorically than can’t.
9. The continuous infinitive is used for an action in progress.
10. The perfect infinitive is used for a past action.

40.

EXAM QUESTIONS

41.

Крылова И. П., Гордон Е. М. Грамматика современного английского языка: Учебник
для ин-тов и фак. иностр. яз. — 9-е изд
Differentiate between the use of “can” and “could”.
§76, §79
What is the basic meaning of the modal verb “can” (followed by the simple
infinitive)?
§77.1-3
What is the equivalent to the modal verb “can”? Specify its usage as the
equivalent of “can”.
§77.1-3
What are the meanings of the modal verb “can”, in which it can be used with all
types of infinitives? In what types of sentences do they occur?
§77.4-5,
§78
What are the ways of expressing strong doubt about negative statements using
the modal verb “can”?
§77.5,
§79
What are the ways of expressing improbability? Specify types of infinitives and
sentences the modal verb “can” is used with?
§77.5,
§79
Enumerate all set phrases with the modal verb “can”. Give Russian equivalents. §81