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'can' and 'could'

Level: beginner

Possibility and impossibility

We use could to show that something is possible, but not certain:

They could come by car. (= Maybe they will come by car.)
They could be at home. (= Maybe they are at home.)

We use can to make general statements about what is possible:

It can be very cold here in winter. (= It is sometimes very cold here in winter.)
You can easily get lost in this town. (= People often get lost in this town.)

We use can't or cannot to say that something is impossible:

That can't be true.
You cannot be serious.

Level: intermediate

We use could have to make guesses about the past:

It's ten o'clock. They could have arrived by now.
Where are they? They could have got lost.

We use could to make general statements about the past:

It could be very cold there in winter. (= It was sometimes very cold there in winter.)
You could easily get lost in that town. (= People often got lost in that town.)

We use can't have or couldn't have to say that a past event was impossible:

They know the way here. They can't have got lost!
If Jones was at work until six, he couldn't have done the murder.

Ability

Level: beginner

We use can and can't to talk about someone's skill or general abilities:

She can speak several languages.
He can swim like a fish.
They can't dance very well.

We use can and can't to talk about the ability to do something at a specific time in the present or future:

I can see you.
Help! I can't breathe.

We use could and couldn't to talk about the past:

She could speak several languages.
They couldn't dance very well.

Level: intermediate

We use could have to say that someone had the ability or opportunity to do something, but did not do it:

She could have learned Swahili, but she didn't want to.
I could have danced all night. [but I didn't]

Permission

Level: beginner

We use can to ask for permission to do something:

Can I ask a question, please?
Can we go home now?

could is more formal and polite than can:

Could I ask a question please?
Could we go home now?

We use can to give permission:

You can go home now.
You can borrow my pen if you like.

We use can to say that someone has permission to do something:

We can go out whenever we want.
Students can travel for free.

We use can't to refuse permission or say that someone does not have permission:

You can't go home yet.
Students can't travel for free.

Requests

We use could you … as a polite way of telling or asking someone to do something:

Could you take a message, please?
Could I have my bill, please?

can is less polite:

Can you take a message, please?

Offers

We use can I … to make offers:

Can I help you?
Can I do that for you?

We sometimes say I can ... or I could ... to make an offer:

I can do that for you if you like.
I could give you a lift to the station.

Suggestions

We use could to make suggestions:

We could meet at the weekend.
You could eat out tonight.

Questions and negatives

We make questions by putting the subject after can/could:

Can I ...?
Could I ...?
etc.
Can you ...?
Could you ...?

 

The negative form is can't in spoken English and cannot in written English.

We sometimes say cannot, but it is very emphatic.

The negative form of could is couldn't in spoken English and could not in written English.

can and could: possibility 1

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can and could: possibility 2

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can and could: other uses 1

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can and could: other uses 2

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Comments

My English grammar says that "could" a less difinite form of can. What is meant by "less definite" form? Does "could" mean "not definite"?

Could is not only past: we also use it as a 'softer’, less definite form of can.

'What shall we do tomorrow?’ ‘Well, we could go fishing.'
When you're in Spain, you could go and see Alex.

Hello Crokong,

As you know, most modal verbs have a number of different uses and can and could are no exceptions. Both can be used to make suggestions:

What shall we do tonight?

We can watch a film if you like, or just go for a drink.

We could watch a film if you like, or just go for a drink.

Could is a little more tentative in these kinds of sentences, I would say, which is probably what your grammar book had in mind.

 

Peter

The LearnEnglish Team

Thanks, Peter. What is meant by "tentative" is to make the speaker sound less dogmatic or open for other opinion. What do you think?

It is not money that can solve children's problems, but love and good teaching.

Is this sentence okay? If it is, then why they didn’t use CAN at the end of the sentence? Like; but love and good teaching can.

Could you please explain it and also give me some examples of this kind of sentence?

Hi amit_ck,

Yes, the sentence is correct! Here is the basic structure, with some examples. 

  • It is not A but B.
  • It's not Jim who I need to see, but Tony.
  • It's not red apples but green apples that she likes.
  • It's not the things I know but the things I don't know that I worry about.
  • It's not money that can solve children's problems, but love and teaching.

A and B are noun phrases (underlined). Can is part of an added clause, not part of the A noun phrase. That's why it's not added to B at the end of the sentence.

You could add 'can' at the end for extra emphasis. In this case, I'd probably say it like this, to separate the two clauses:

  • It's not money that can solve children's problems. Love and teaching can.

I hope that helps :)

Jonathan

The LearnEnglish Team

Dear Team,
I have some confusion about the possibility of can and could.

It says 'can' is used with general statements
while 'could' is used when it is possible but not certain. Then,
1) You can be lost in town.
2) You could be lost in town.
1.What is the difference between these two sentences.

And my teacher once said 'can' is used with strong possibility while 'could' is with less one. 2.Is that correct?

From my point of view, it all depends on the speaker's view which he considers one as a certain thing, he might use ' can ' and one as not a certain thing , he might use ' could '.
3.Is mine correct?

Hello DaniWeebKage,

Your first sentence is not correct as it appears to describe a current situation (being lost); this would mean that you are speculating rather than describing what is generally possible. Note that in the example on the page the verb is 'get lost', which does not describe a current state. Your second sentence is fine. It expresses speculation about the present and has a similar meaning to 'maybe' or 'perhaps'.

 

You can get lost easily in this town. [a general statement about the town: it is possible because the town's layout is confusing]

You could get lost easily in this town. [a specific statement about your trip: there is a chance of this happening]

 

Peter

The LearnEnglish Team

Thanks a lot, Sir Peter,
1)In which situation should be use 'You can be lost in this town" ?
2) Does 'Can' mean more possibility to happen than 'could'?
All the best.

Hello again DaniWeebKage,

We wouldn't use this formulation. To speculate about what may or may not be true at the moment we use could (You could be lost).

Can describes something which is not impossible. Of course a person can be lost, but it is a banal statement without any real meaning.

 

Think about it this way: when we are talking about how a person feels we say 'He could be angry', meaning 'there is a chance he is angry'. We don't say 'He can be angry' because it is obvious: anyone can be angry at any time.

 

Peter

The LearnEnglish Team

Can we say "Could" is used for Future possibility ?

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