Can/could

Can/could express ability, which may be natural or learned:
present reference: I/You/He (etc.) can/can t hear music

past or perfect reference I/You/He (etc) could/couldn 't play chess

I/You/He (etc) could have/couldn't have danced all night
future reference: None. We use will be able to [but compare > 11.19, 11.26]

Verbs and verb phrases related in meaning to can (ability):

be (un)able to I am (not) able/1 am unable to attend the meeting

be (in)capable of He is (not) capable/He is incapable of doing the pb

manage to: We managed/didn 't manage to persuade him to accept

succeed in They'll succeed/won't succeed in getting what they want

11.11 'Can' = ability: the present

11.11.1 'Can' + verb (natural ability)

Natural ability can be expressed as follows: Can you run 1500 metres in 5 minutes? (= Are you able to run? Are you capable of running?) / can/cannot/can't run 1500 metres in 5 minutes

Can and am/is'are able to are generally interchangeable to describe

natural ability, though able to is less common: Billy is only 9 months old and he can already stand up Billy is only 9 months old and he is already able to stand up

However, am/is/are able to would be unusual when we are

commenting on something that is happening at the time of speaking: Look' I can stand on my hands¹

Modals.etc to express ability

11.11.2 'Can' + verb (learned ability or 'know-how')

Learned ability can be expressed as follows:

Can you drive a car?

(= Do you know how to? Have you learnt how to?)

/ can/cannot/can't drive a car Verbs such as drive, play, speak, understand indicate skills or learned,

ab.ht.es .Can, and to a lesser extent, am/is/are able often combine with such verbs and may generally be used in the same way as the simple present tense:

/ can/can't play chess (= I play/don't play chess)

11.12 11.12.1

'Could/couldn't' = ability: the past

Past ability (natural and learned) expressed with could'

Could, couldn't or was/were (not) able to can describe natural and

learned ability in the past, not related to any specific event: Jim could/couldn't run very fast when he was a boy Barbara could/couldn't sing very well when she was younger Jim was able to/was unable to run fast when he was a boy,

We also often use used to be able to to descr.be past abilities / used to be able to hold my breath for one minute under water

Could and was (or would be) able to occur after reporting verbs He said he could see me next week.

For 'unreal past¹ could (= was/were able to) after if [> 14.10-12, 14.14

11.12.2

The past: could' + verb: achievement after effort

Could and was/were able to can be interchangeable when we refer to the acquisition of a skill after effort:

11.12.3

/ tried again and found I could swim/was able to swim Specific achievement in the past

Could cannot normally be used when we are describing. the successful completion of a specific action; was/were able tn managed to or succeeded in + ing must be used instead

were able to rescue In the end they managed to rescue the cat on the ronf succeeded in rescuing

If an action was not successfully completed, we may use couldn't. They tried for hours but they couldn't rescue the cat (or weren 't able to, didn t manage to etc)

Could can be used when we are asking about a specific action (as opposed to describing it):

Could they rescue the cat on the roof? (= did they manage to?)

- No, they couldn't It was too difficult However, an affirmative response requires an alternative to could

- Yes, they managed to (Not 'could')

11.13

Can/could' + verbs of perception [> APP 38.4]

Verbs of perception [> 9.3], like see hear, smell rarelv occur progressive Can, and to a lesser extent, am/is/are able to combine

11 Modal auxiliaries and related verbs

with such verbs to indicate that we can see, hear, etc. something
happening at the moment of speaking. In such cases can has a
grammatical function equivalent to the simple present in statements
and to do/does in questions and negatives:
/ can smell something burning (= | smell something burning.)
/ can't see anyone (= I don't see anyone.)

Could can be used in place of the simple past in the same way: / listened carefully, but couldn't hear anything (= I listened carefully, but didn't hear anything.) Can/could can be used with verbs suggesting 'understanding': / can/can't understand why he decided to retire at 50 I could/couldn't understand why he had decided to retire at 50. Can't/couldn't cannot be replaced by the simple present or simple past when conveying the idea 'beyond (my) control' (impossible): / can't (couldn't) imagine what it would be like to live in a hot climate. (Not */ don't/I didn't imagine*)

11.14 'Could' and 'would be able to'

We can use could as an 'unreal past' [> 14.10, 14.14] in the sense of 'would be able to'. When we do this, an /f-clause is sometimes implied:

I'm sure you could get into university (if you applied) Could + never has the sense of 'would never be able to':

/ could never put up with such inefficiency if I were running an

office (i.e. I would never be able to) Could is often used to express surprise, anger, etc. in the present:

/ could eat my hat I could slap your face!

11.15 'Could have' and 'would have been able to'

We do not use can/can't have + past participle to express ability or

capacity. We use them for possibility or conjecture (He can't have told

you anything I don't already know) [> 11.32].

However, in conditional sentences and implied conditionals we may

use could have + past participle (in place of would have been able

to) to refer to ability or capacity that was not used owing to personal

failure or lack of opportunity [> 14.19]:

If it hadn't been for the freezing wind and blinding snow, the

rescue party could have reached the injured man before nightfall

For could have (= had been able to) in conditions [> 14.16-17].