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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.


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]


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.


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?


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.


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 ...?
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


can and could: possibility 2


can and could: other uses 1


can and could: other uses 2




Can you give me a summary for this lesson,please?

Hi there,

Talking about "ability" what's the difference between "manage to" and "succeed in"? And how can they be compared to "can" or "be able to"?

Thanks in advance. You're the best, guys.

Hello Knightrider,

'Manage to' suggests that the activity was successful but difficult. 'Succeed in' suggests only that it was successful, but does not tell us if it was difficult or not.

'Can' is used for general ability, not specific achievements. 'Be able to' can be used for both general ability and specific achievements, but does not tell us if the task was easy or difficult.

I hope that clarifies it for you.

Best wishes,



The LearnEnglish Team

Everything's clear now, Peter. You've been most helpful. Thank you.



May I know whether the use of "could" in the following sentence is correct?

"Go and ask him whether he could differentiate the two."

If incorrect, could you please advise me the correct way to say it?

Thank you.

Hello Pocoyo,

That sentence is correct.  You could also use 'can' in the sentence, with a different meaning: 'could' implies a hypothetical situation in the sense that the person will not have to do it, and your question is purely speculative, while 'can' implies a real situation and that you want the person to try to differentiate between the two items for you.

Best wishes,



The LearnEnglish Team 

Hello Peter,

Thank you very much for your explanation! : )

there can be storm
there could be storm
the second one is used for uncertain situations.You said that can is used for possible situations..and the meaning of possible is "that may exist or happen, but that is not certain". So that means both can and could expresses possibility...So wats the difference between these two above sentences ???

Hello chatterjee,

The difference between "There can be storms" and "There could be a storm" is that the first sentence is talking in general about the climate in a place. For example, on Mt. Everest, there can be storms (at any time of the year). Here the sentence is about the climate there in general.

"There could be a storm" would be used to refer to a specific occasion. For example, if you're planning a trek to the Mt. Everest base camp and are thinking about what gear to take, you might want to take raingear as "there could be a storm" while you are on your trek. Here you're talking about a specific trek, not the climate in general.

As you can see, there is not really a difference in meaning here - it's more a question of use. I hope this helps you.

Best wishes,
The LearnEnglish Team

sir as you said that can is used for general statements which are possible..Does this mean that "can" is used for showing 100 % surety..
For example - Using mobile phones while driving can be dangerous...Does this means that using mobile phones might be dangerous (more that 50% dangerous) or does that mean it is 100 % dangerous..??
As you said that can and could both are used to express possibility and could is used for uncertain...So does can expresses definite situations (100% possibility) or does it expresses a situation which is very likely to get happened (more possible than could but not 100% ) ???

i googled the meaning of possible and found that possible means "that may exist or happen, but that is not certain or probable." So possible in itself means why can is not used for uncertain situations...
Can i say that can expresses more possibility than could but not 100 % possibility.
For example -
1) There could be a storm later. (30-40 % possibility)
2) smoking can cause cancer. (70 % possibility but not 100 %)
Conclusion - can expresses more possibility compared to could but it does not expresses 100% possibility....Am i right ???