can or could

 

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

Comments

hello sir could you pls tell me, what is the difference b/w "can be find and can be found" with examples

Hello anuj,

'can be find' is not correct and 'can be found' is correct. It's the modal verb 'can' plus a passive infinitive.

All the best,
Kirk
The LearnEnglish Team

is this sentence is correct?

we are waiting for the power, so we could microwave our dinner.

Hello helpinspeaking,

I would say that 'can' is needed here, as 'could' would refer to the past in this context. You could also say 'will be able to'.

Best wishes,

Peter

The LearnEnglish Team

Hello helpinspeaking,

It says just that on the page:

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

Best wishes,

Peter

The LearnEnglish Team

Hi there!
Is this sentense true?
(as a child my life could be streesful.)
Regards

Hello smsahand,

'As a child my life could be stressful' is grammatically correct (good work!), but only you can tell us whether it's true or not! ('true' means 'accurate' - see the dictionary.)

All the best,
Kirk
The LearnEnglish Team

Hi, I want to know why 3rd form of find is used in below sentence. I mean which grammar is that.

The typhoid bacteria can be found in contaminated food or water.

tnx

Hello AK47,

'can be found' is a passive construction consisting of the modal verb 'can' and the bare infinitive of the verb 'find' in the passive voice. On the pages that I've linked to, please note that 'found' is called a past participle - this is just another name for 'third form'.

Best wishes,
Kirk
The LearnEnglish Team

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