can, could and could have


Questions and negatives:

We make questions by putting the subject after can/could:

Can I …? Can you …? Could I … Could you …? and so on.

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.
We sometimes say could not.

We use can and can’t :

  • To talk about ability:

Maria can speak four languages.
I can’t swim, but my sister can.

  • To say that something is possible or impossible:

Learning English can be difficult [= Learning English is sometimes difficult.]
Children can be very naughty [= Children are sometimes very naughty.]
It’s still light. It can’t be bedtime.

  • For requests and refusals of requests

Can I go home now?
You can go whenever you like.
You can borrow the car today, but you can’t have it tomorrow.

  • To offer to help someone:

Can I help you?
Can I carry that bag for you?

We use could and couldn’t as the past tense of can/can’t:

  • To talk about ability:

I could run very fast when I was younger.
She couldn’t get a job anywhere.

  • To say that something was possible or impossible:

Our teacher could be very strict when we were at school. [= Some teachers were very strict.]
People could starve in those days. [= People sometimes starved.]
You couldn’t use computers in the nineteenth century.

  • To make a polite request:

Could I go now please?
Could you lend me a dictionary please?

  • To make a polite offer:

Could I give you a lift?
I could carry that for you.

We use could have:

  • to show that something is possible now or was possible at some time in the past:

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




Hello guys. Greetings to the England. I have searched for the explanation of (could have) and i guess i have it.
Could - this is the FACT which says that (something) was able to do something in the past.
Could have - this is the SUPPOSITION which says that something could have happened in the past, but it didn't happen.
The first sentence: When i was at school i could run quickly.(I was able to run quickly)
The second sentence: When i was at school i could have run quickly.(But i didn't) - SUPPOSITION.
1.Could have = 2.(would can) - the second isn't use i guess, but it helps to understand the first.

Hello rewand,

Both 'could' and 'could have' have multiple uses, as shown on this page. While there are core notions behind each, I would advise against oversimplifying in this way. Trying to find an overly simple rule results in a mass of exceptions and confusion, in my experience.

Best wishes,


The LearnEnglish Team

I can understand the meaning of could have.....but i didn't understand the use of could have been.....??? Or its meaning....kindly guide about that.....

He could have been prime minister now, if he had not decided to leave politics.

What's "could have been" showing/explaining here........because word "been" always makes me confuse....advice me on that....

Hello Touqeer,

'been' is the verb 'be' here, used with 'could have'. 'could have been' is being used here in the way described at the bottom of this page, i.e. to describe something that was possible in the past, but which did not happen. 

I hope this helps.

By the way, just so you know, eventually we will answer your other questions, but in general, please take some time to look for answers yourself before asking here. We're happy to answer questions, but doing so is only part of our work and we get many comments every day. We simply can't answer more than one question per user per day.

Best wishes,
The LearnEnglish Team

Hello Touqeer younas,

Can you provide an example sentence please? We'll be happy to explain, but the context is necessary.

Best wishes,


The LearnEnglish Team

Hello! could someone please help me? I need to know if is it correct to use could and need in the same sentence, eg. how could i need an umbrella when it is not raining.

Hello Mariah,

Yes, you can use them together – the sentence you asked about is correct.

Best wishes,
The LearnEnglish Team

Thanks to all teachers of this site. Not long time ago i asked about difference between (could have) and (could) the both these are in the past. And i obtained the answer that the ('could have' is used to speak about a specific instance of being able to do something, but not doing it.). And ('could' refers to a very general past ability, not to a specific situation.) May i ask you to give me the example of the (general past ability) and (specific past ability) with using of COULD HAVE and COULD as in the past. Thanks beforehand)