Possibility

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.

Impossibility:

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.

Ability:

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.

 

Permission:

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.

 

Exercise

Section: 

Comments

Hello Mr.Kirk & Mr. Peter, I hope you are doing great.

I'm practicing English for few years but yet I've more doubts. I would like to know which of these correct and situational meanings about "What can I do for you?" & "What I can do for you" .. Please tell me which is correct and when to use it, I know more people using more often the second one in India alike "What will I do?" & "What I will do?" . Please reply the correct sentences.

Hello sangeetha01,

If you intend to ask a question then 'What can I do for you?' and 'What will I do?' are the correct forms.

 

Best wishes,

Peter

The LearnEnglish Team

Sir,

Please explain 'could be' can it be used as past tense. Example "century ago America and Russia could be using hundreds of spies to Snoop down themselves"

Regards

Hello raji,

'Could' is the past tense of 'can', as the page says. However, your sentence does not represent a good use of 'could'. I'm not sure what you are trying to express there - that this was possible in the past but is not now? I'm afraid it's not clear to me.

 

Best wishes,

Peter

The LearnEnglish Team

Im little bit confused with can.in the sentence it can be very cold in winter.
What is the general thing in this sentence.can u give some more examples for can in possibility also explaining the general element of lt..

Hello jino,

As it says, this use of 'can' means 'it sometimes happens' or 'it's not impossible'. Here are some more examples:

Be careful when you speak to Mr. Jones. He can be irritable! [= sometimes he is irritable]

Drive carefully in London. It can be quite dangerous. [= sometimes it is dangerous]

 

Best wishes,

Peter

The LearnEnglish Team

Hello sir, could you please tell me how to use can/could for invitations (with example)
Thank you.

Hello mmoaazhameed,

When the explanation above says 'offers and invitations', 'invitation' means essentially the same thing as 'offer'. So, for example, you could say to a person who looks lost on the street: 'Can I help you?' or 'Could I help you?' – these are offers or invitations to help.

Our sister site LearnEnglish Teens has a video that explains this grammar as well as a few additional practice exercises if you'd like to work on this more.

All the best,
Kirk
The LearnEnglish Team

i have an other question. are both formations correct?

"the best you could say" vs "the best you can say"?
( you could say to a person who looks lost on the street or you can say........?)

Hello mmoaazhameed,

I'm not clear on the context of the sentence. Is this part of a dialogue? Has the person on the street asked you something? Before we can answer we need to know the context, as this is crucial in determining whether 'can', 'could' or both are correct.

 

Best wishes,

Peter

The LearnEnglish Team

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