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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.
I couldn't see you.

Ability: can and could 1


Ability: can and could 2


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]

Ability: could have 1


Ability: could have 2



Hello Rita Rihani,

This is really a question for your teacher rather than for us. We don't usually provide answers to test questions or homework tasks because the answer may depend upon the syllabus or certain instructions provided. However, the most likely possible answer here would be 'It couldn't be Tom who/that you saw yesterday. He has gone to Italy'.


Best wishes,


The LearnEnglish Team

Thank you for answering ! I appreciate your help!

can 'have to' only be used as the past form of 'must'? I mean, can't it be used as an alternative to it: 'You must wear a safety helmet' 'You have to wear a safety helmet'? Are there any differences in meaning?
Thanks in advance

Hello l.audisio,

'Have to' can be used instead of must as you suggest:

I must go now.

I have to go now.

There is a slight difference in meaning. We generally use 'must' when the obligation is a personal one: the obligation comes from us. We tend to use 'have to' when the obligation is external, from a rule or organisation, for example.

Note that this page deals with 'ability, permission, requests and advice', not obligation. You can find more information on the distinction between 'must' and 'have to' on this page.


Best wishes,


The LearnEnglish Team

Hi Sir,
Please tell me, what is the difference between following sentences.

I have lived here for 20 years.

I have been living here for 20 years.

As I understand, In the first sentence, I lived there for 20 years but now I am not living there. ??

In the second sentence , I am living there for 20 years nd still living ?

Sanjay Singh

Hello sanjay,

Please see our Present Perfect Simple and Present Perfect Continuous page to learn more about this. If the answer to your question is still not clear after that, please feel free to ask us again on that page.

Best wishes,
The LearnEnglish Team

Hi Sir,
Im confused about use of could, sometimes it use for past tense and sometimes it use for present tense like u have used for present tense in these examples -
1- Could I ask a question please?
2-Could we go home now?

Sir, Please tell me how to change these two sentences in past with use of could. And also clarify the use of could in present and past tense.

Hi singh singh,

These are both requests, and to make them requests in the past we would use a perfect modal - 'could have':

Could I have asked a question (then)?

Could we have gone home then?

However, the present and past forms depend on the meaning for which 'could' is used. The examples above are requests and there are similar past forms for permission, but if we talk about ability then we have different forms for present and past:

I can swim. (present)

I could swim. (past)


Best wishes,


The LearnEnglish Team

Thanks a lot Sir !


I would like to know if its following sentence is correct?
'With pleasure, I would to confirm my arrival day' .Thanks in Advance