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

Hello niranjankumar47,

Yes, you can, with the same meaning.

Best wishes,
Kirk
The LearnEnglish Team

Can 'could' be used to express a wish ?
e.g. I'll be happy if I could do half as much as you did (speaking of something that is yet to be done)

Have 2 questions here.

She couldn’t get a job anywhere.

May I know is it the meaning of this sentence is previously she couldn't get a job, but now she can. Am I correct?

I still don't understand how to use past tense, could we use past tense when something happened in the past but we are not sure whether it still happen now?

For example, She liked to eat orange. We knew she liked orange, but now we don't know. In this circumstance, should we use past or present tense

Thank you.

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,

 

Peter

The LearnEnglish Team

hello!!
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,

 

Peter

The LearnEnglish Team

hello!!
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 state...how?

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