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

Hello arthurlocke,

As I said in my earlier reply, there is no grammatical problem with using 'can' in these ways. Provided the context is appropriate, you can use 'can' with both simple and continuous infinitive forms:

After so many arguments, can they be meeting tomorrow?

As far as I know, she is still in Japan and he is in London. Can they be meeting tomorrow?

Can they be meeting tomorrow? Four members of the board are sick, so I don't see how there can be a quorum.

 

The British Council does not recommend publications as we have a policy of neutrality with regard to publishers. As far as resources go, other than this section on our site, there are many grammar books available from the major publishers. The best way to choose is to visit a good bookshop and take a look at several grammar books so you can compare entries on the same topic to see their levels of detail and clarity of explanation side by side.

 

Peter

The LearnEnglish Team

Hello arthurlocke,

I think it's perfectly fine to use 'can' in all of those situations in terms of grammar. The reason some examples seem less convincing is, I think, rather the result of it being difficult to imagine an appropriate context rather than a grammatical issue. For example, all of these sentences are perfectly fine:

Can it rain on Mars, or is it too cold and dry?

Can the match really be happening tomorrow? There's a transport strike, it would be ridiculous!

 

Peter

The LearnEnglish Team

So, what goes in "She could help if she _____.(can,could)"?

Hello Ashmin,

I'm afraid neither answer sounds right to me. Perhaps 'She would help if she could'?

All the best,
Kirk
The LearnEnglish Team

Dear sirs,

I have read somewhere that we can use "may / might have done" even when we are talking about the future. There were no examples given. If the information is correct, will you be kind enough to explain and examplify it. I would be grateful if you would also tell me if the case for "could have done" is the same or not. Thank you in advance.

Hello arthurlocke,

It is possible to use perfect modal verbs with a future meaning provided you have a future point in time from which you are looking back. The so-called future perfect form (will have done) is an example of this bith other modal verbs can be used in place of will, so long as the context is suitable. For example:

We will have finished it by Thursday. That's a promise!

We might have finished it by Thursday, but that's impossible now.

We could have finished it by Thursday, if not for your mistake.

 

Peter

The LearnEnglish Team

Sir..
What is difference between two sentence
"They could arrived now"
"They could have arrived know"

Hello dhana,

Neither sentence is correct.

In the second sentence the last word should be, I guess, 'now' rather than 'know''. In this sentence the speaker is speculating about the present. They are guessing that the people ('they') are probably already at their destination.

The first sentence is not correct. We do not use a past form after 'could', so you cannot say 'could arrived'.

 

Peter

The LearnEnglish Team

Hi, learnenglish!

I would like to ask a question regarding "can/could".
I had an essay assignment, and in that essay, I wrote "Everyone in my family counted on television, either for keeping on top of news or for entertainment. In addition, I also could not forget the joy when I watched morning cartoons."

But, my teacher revised it and she told me that it should be "In addition, I also cannot forget" instead of "could not forget".

My question is, why "I cannot forget" is the correct answer where in fact I talked about something in the past.

Thank you for replies.

Hi araisin,

If possible, you should ask your teacher, but I imagine she was thinking that the action of remembering (not forgetting) is in the present time. In other words, the things that you remember are in the past, but the action of remembering them is in the present. Does that make sense?

All the best,
Kirk
The LearnEnglish Team

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