Can and could are
used in a variety of different ways for different purposes. We can use them to
talk about ability and possibility, to make requests and to ask for permission.
Can and could:
to express ability
Here the
distinction of can for present scenarios and could for past situations are
preserved:
He could read by
the time he was four years old and now he can speak six languages fluently.
I couldn't find my
Tom Jones CD when I was looking for it the other day, but now I can see that you have it.
Can and could / will and would: to make
requests
When making
requests, can and could are both used to refer to present and future
situations. When we are asking something of others, will and would are also
commonly used alternatives. Compare the following:
Could I have
another cup of tea, please?
Can I have some
more tea, please?
Could you pick
Lauren up from school for me this afternoon, please?
Can you pick up
Lauren from school for this afternoon, please?
Would you collect
Lauren from school for me this afternoon, please?
Will you fetch
Lauren from school for me this afternoon, please?
Note from the
above examples that could and would sound marginally more polite than can and
will.
Note that if we
are talking about ability to do something, rather than making a request, it
will be necessary to use will be able to talk about future ability:
Will you be able
to pick Lauren up from school this afternoon by any chance?
Note also that if
we want to sound particularly polite when making a request of others, we can
use the would you mind + verb-ing construction:
Would you mind
picking Lauren up from school? ~ No, I don’t mind. It’s no trouble.
We can also use
will to express the speaker’s willingness or intention to do things:
We haven’t got any
paper for the photocopier. ~ I’ll get some for you.
Can you lend me
fifty pounds for the weekend? I’ll pay you back on Monday.
Can and could:
to ask for and give permission
Can is more
commonly used than could in these contexts. May is a further alternative:
Can / May I help
you with that? ~ Yes, you can.
Can / May I carry
that for you? ~ Yes, you may.
Can I enter the
room while the recording is in progress? ~ No, you may not.
Can I listen to it
afterwards? ~ No, you can’t.
Note in the
example above that we cannot use couldn’t when refusing permission.
Reported speech
In reported
speech, would and could or would be able are used after reporting verbs in the
past tense where will and can are used in direct speech. This is because there
is a difference in time, place and speaker:
I’ll tell Mary
about the meeting you’ve arranged for next Saturday.
He said he would
tell Mary about the meeting tonight, but she’s not here yet.
I can look after
Jenny if you’re busy.
He said he would
be able to look after Jenny if I was busy.
However, would and
could do not change in reported speech, if they are already present in direct
speech:
It would be great
if you could come to Manchester too.
He thought it
would be great if we could go to Manchester as well.
Conditional
structures and future situations
To talk about
things that will probably not happen, we use a past tense in the if-clause and
would, or sometimes could, in the main clause. Compare examples above and
below:
If I knew where
she was living now, I would tell you. But I don’t know.
To talk about
things that may happen in the real future, we use a present tense in the
if-clause and will, or sometimes can, in the main clause:
I’ll try and
repair your bike tomorrow, if I have enough time.
I’ll try to mend
your bike tomorrow, if I can find enough time.