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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.

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

Hi teachers,

1. Her colleagues could not fault her dedication to the job. --> Assuming that this sentence is not talking about the past, could I change "could not fault" to "cannot fault"?

2. The doctor examined her carefully but could find nothing wrong. --> could I delete "could" in this sentence? (i.e. ...but found nothing wrong.)

Thank you.

Hi patph0510,

1. 'Could' is referring to the past in this sentence. To say something is impossible in the present, we use 'can't' – but not 'couldn't' (see the first section above for some examples). So, your sentence with 'cannot fault' is the correct one for the present meaning.

2. Yes, you could. The meaning would be very similar, but with one difference: the version with 'could' includes the meaning of the doctor attempting or making effort to find the problem. The version without 'could' doesn't include that, and is focused on the end result (finding nothing wrong).

Best wishes,

Jonathan
The LearnEnglish Team

Hi teacher,

In the following two sentences, could I use "could" instead of "would"? Would there be any difference in meaning?

1. Would you lend me the car tomorrow night, Dad?
2. Would you fill in this form, please, sir?

Thanks.

Hi teachers,

Not sure if you have missed my question. I would appreciate it if you could give me a reply.

Thanks!

Hello brian1010,

Yes, somehow we missed your question -- sorry about that!

In both sentences, some might argue that 'would' speaks more of willingness and 'could' speaks more of ability, but in most cases, both forms would be correct and mean the same thing.

All the best

Kirk

The LearnEnglish Team

Could you please tell me the difference between : I might be able to come today vs I might come today

Hello Ballou1982

The first one implies that the main thing is whether you can or cannot come today. You don't know yet if something might stop you from coming. For example, if your friend has invited you to visit him, but you think you will have to work, you could say this because if you have to work, you can't visit your friend.

The second one is less specific. It just says that perhaps you will come or perhaps you will not. It could be due to work, it could be because you don't want to, it could be anything, really, that prevents you from coming.

Hope this helps.

All the best

Kirk

The LearnEnglish Team

Hello teachers,
I am back with a question.
It is about "Later" and "Later on".
The difference, though being distinct to me, can sometimes get me.
I am sure u can help me with its distinction precisely.

Could you tell me when to use " later" and "later on"?

Hello GIRIKUMAR,

As far as I am aware, there is no difference in meaning. Later on is a little more informal.

Later is often used as an informal way of saying goodbye, with the same meaning as See you later.

 

Peter

The LearnEnglish Team

Hello teachers, hope you are all doing great.
In the Oxford dictionary, the meaning of the phrasal verb "mess up" has the verb 'fail' not with the preposition 'in' but 'at' when it's supposed 'in' as regards one of the examples below the first meaning concerned with the verb 'fail' in the same dictionary.

The sentence goes thus,
Mess up: to fail at something or do it badly.

My question is,
What's the difference between "fail in" and "fail at"?
When should we you 'at' and 'in' with the verb 'fail'?
Thank you, teachers.

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