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

It can be very cold in winter. (= It is sometimes very cold in winter)
You can easily lose your way in the dark. (= People often lose their way in the dark)

We use could as the past tense of can:

It could be very cold in winter. (=Sometimes it was very cold in winter.)
You could lose your way in the dark. (=People often lost their way in the dark)

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

If we don’t hurry we could be late. (=Perhaps/Maybe we will be late)

We use could have to show that something is/was possible now or at some time in the past:

It’s ten o’clock. They could have arrived now.
They could have arrived hours ago.


We use the negative can’t or cannot to show that something is impossible:

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

We use couldn’t/could not to talk about the past:

We knew it could not be true.
He was obviously joking. He could not be serious.


We use can 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 to talk about the ability to do something at a given time in the present or future:

You can make a lot of money if you are lucky.
Help. I can’t breathe.
They can run but they can’t hide.

We use could to talk about past time:

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



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 if you like.
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 free.

Instructions and requests:

We use could you and 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 and invitations:

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 can give you a lift to the station.




Dear sirs, although I have been trying to find out if I can use "Can ...?" question form to ask about possibility, I was not able to arrive at a conclusion if it could be used in some kinds of statements. It seems it can always be used specifically if the verb is a stative one (as in "Can he know George?" and not if the verb is a dynamic one (as in "Can it rain tomorrow?"). Again, it seems that we can use it only in the present progressive denoting "now" (as in "Can he be having a bath at this time of day,") but not in a present progressive statement denoting future (as in that personal arrangement question, "Can they be meeting tomorrow?" I figured these out, not based any information, but by examining the examples I came across on the web? I am not sure if I am right. Will you please illuminate me about the matter? Thank you in advance. Best regards.

Dear sir, do you mean we can say "Can it rain tomorrow?" / "Can they be meeting tomorrow?". I wanted to know if "can" behave differently when used with dynamic vs stative verbs and with present continuous vs future present form of the present simple. As far as I understand, "Can he be having a bath at this time of day?" is true but "Can they be meeting tomorrow?" is wrong. Am I right? If I am, will you please let me know the differences between the questions. If I am not right, will you please recommend me a few sources that could let me understand the uses of modal verbs thoroughly. Thank you in advance.

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.



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!



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,
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.



The LearnEnglish Team

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'.



The LearnEnglish Team