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.

 

Exercise

Comments

Could anyone please explain can we use could be in present tense..............

Hi Learner S,

Could you please give an example of what you mean? could has many uses and meanings, and I'll be able to answer your question better if I understand what you're asking.

Best wishes,

Kirk
The LearnEnglish Team

Hello OsamaAnischawla,

'Would' is one of the modal verbs in English and can be used in a number of different ways.  To investigate modal verb and their various meanings and uses, go to this page and work through the pages which are linked near the top, including one on modals + have.

I hope those links help to clarify it for you.

Best wishes,

 

Peter

The LearnEnglish Team

Hello there!

He could be the next champion.
It could be very cold in winter.

Are those two sentences describing future time?

Thank you.

Hello bimsara,

The sentences can be seen as describing both a present possibilty (he has now the potential to be the next champion) and a future possibility (when he will or may be champion) - it is very much a question of how you look at it.  In a sense, all sentences which describe probability or possibility reference the future, but they are also describing a present state (potential).

I hope that helps to explain it for you.

 

Best wishes,

 

Peter

The LearnEnglish Team

I am confused how to use shall / will, please help me

Hello smile 1989,

Both 'shall' and 'will' are modal verbs usually used with a future meaning and you can find more information on how to talk about the future here.  However, 'shall' is no longer used very often in English.  Nowadays, it is used mainly in very polite questions ('Shall I take your coat, Sir?'), in some legal documents or for rhetorical effect (a politician giving a speech may choose to use 'shall' instead of 'will').  In normal conversation it is extremely unusual and would sound old-fashioned and quite unnatural in modern English to most people.

Best wishes,

 

Peter

The LearnEnglish Team

Good morning sir, i know that "could" is the past tense of "can" and "have arrived" is the present perfect of "arrive" but i don't understand the tense of this sentence "They could have arrived hours ago." .
thank you forward.  

Hello kaystomy,
It's better to think of 'could have' as a phrase by itself, rather than as a combination of the kind you suggest.  It is an example of a perfect modal verb and, like all modal verbs, it is used with a number of different meanings.  As the information on the page says, 'could have' is used to describe something which was possible at some time in the past - they could have done it (it was possible) but we do not know if they actually did or not.
I hope that clarifies it for you.
Best wishes,
 
Peter
The LearnEnglish Team

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