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 stevencch,

As I said in reply to your earlier question on this, the past tense does not tell us either way about the present; for this, we rely on the context.  Your first example does not tell us whether or not she can get a job now - it only tells us about the past situation. Similarly, the sentence 'She liked to eat oranges' does not tell us anything about whether or not she likes oranges now.  Again, the context is necessary for us to form an opinion on this.

Best wishes,



The LearnEnglish Team

how r u sir
sir i need some help , could u plz explain me where do we use "can have"

Hello OsamaAnischawla,

As a perfect modal, 'can have + past participle' is very rare in English.  It is used to speculate about the past, but only in questions and negatives:

Can he have forgotten about what you said?

She can only have decided that she's not interested - there's no other explanation.

Adverbs such as 'only', 'hardly' and 'never' are often used in these sentences.

I hope that clarifies it for you.

Best wishes,



The LearnEnglish Team

how r u sir
sir i need some help , could u plz explain me where do we use "can have"

Hi sir
I bit confuse in using ''could be''in present tense............
He could be the one who stole money........
In other grammar book this sentence is explained as a present

Hi Learner S,

'Could' is the past form of 'can'.  It is a modal verb and though it can have a present meaning, as in your example, it is formally a past form.  This is because in English we use past forms for more than just past time.  We can use them to show politeness ('Could you pass me the sugar?' is a little more polite than 'Can you pass me the sugar?'), to show that something is not likely ('If you could help me, that would be great' is less certain than 'If you can help me, that will be great'), amongst other uses.  That is why talking about 'could be' as a present tense is not accurate.

To learn more about different modal verbs, including 'could', visit this page.  You'll see links there to pages about specific modals and meanings.

Best wishes,



The LearnEnglish Team

sir, i m confuse about where to use would and would have
could you plz guide me ???

Hello OsamaAnischawla,

Your question was answered the first time you asked it (see further down the page).  Please post questions once only - sometimes it takes us a little while to answer them, but we can't do it any quicker, no matter how many times the question is asked.

Best wishes,



The LearnEnglish Team

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