Friday, 2 July 2010

can and could: forms, ability

can and could: forms


1 Can is a 'modal auxiliary verb' .  There is no -s in the third person singular.

  • She can swim very well (NOT She cans . . .)


Questions and negatives are made without do.

  • Can you swim?(NOT Do you can swim?)

  • I can't swim. (NOT / don't can swim.)


After can, we use the infinitive without to.

  • I can speak a little English. (NOT / can to speak . . . )


2 Can has no infinitive or participles. When necessary, we use other words.

  • I'd like to be able to stay here. (not . . . to can stay . . .)

  • You'll be able to walk soon, (not You'll can ... .)

  • I've always been able to play games well. (not I've always could . . .)

  • I've always been allowed to do what I liked. (not I've always could . . .)


3 Could is the 'past tense' of can. But we use could to talk about the past, present or future.

  • I could read when I was four.

  • You could be right.

  • Could I see you tomorrow evening?


Could also has a conditional use.

  • I could marry him if I wanted to. ( = It would be possible for me to marry him . . .)


4 Contracted negative forms  are can't (/ka:nt/) and couldn't (/'kudnt/).
Cannot
is written as one word.

5 Can and could are used in several ways. The main uses are:

  • a   to talk about ability

  • b   to talk about possibility

  • c   to ask, give and talk about permission

  • d   to make offers and requests, and to tell people what to do.


can and could: ability


1 Present

We use canto talk about present or 'general' ability.

  • Look! I can do it! I can do it!

  • I can read Italian, but I can't speak it.


2 Future

We use will be able to to talk about future ability.

  • I'll be able to speak good English in a few months.

  • One day people will be able to go to the moon on holiday.


We use can if we are deciding now about the future.

  • I haven't got time today, but I can see you tomorrow.

  • Can you come to a party on Saturday?


3 Past

We use could for 'general ability' — to say that we could do something at any time, whenever we wanted. (Was/were able to is also possible.)

  • She could read when she was four. (OR She was able to ... )

  • My father could speak ten languages.


We do not use could to say that we did something on one occasion. We use managed to, succeeded in . . . -ing, or was able to.

  • How many eggs were you able to get? (NOT . . . could you get?)

  • I managed to find a really nice dress in the sale yesterday. (NOT I could find . . .)

  • After six hours' climbing we succeeded in getting to the top of the mountain. (NOT . . . we could get to the top . . .)


But we can use couldn't to say that we did not succeed in doing something on one occasion.

  • I managed to find the street, but I couldn't find her house.


4 Conditional

We can use could to mean 'would be able to'.

  • You could get a better job if you spoke a foreign language.


5 could have ...

We use a special structure to say that we had the ability to do something, but did not try to do it.

could have + past participle




  • I could have married anybody I wanted to.

  • I was so angry I could have killed her!

  • You could have helped me — why didn't you ?

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