'can' and 'could'

Level: beginner

Possibility and impossibility

We use could to show that something is possible, but not certain:

They could come by car. (= Maybe they will come by car.)
They could be at home. (= Maybe they are at home.)

We use can to make general statements about what is possible:

It can be very cold here in winter. (= It is sometimes very cold here in winter.)
You can easily get lost in this town. (= People often get lost in this town.)

We use can't or cannot to say that something is impossible:

That can't be true.
You cannot be serious.

Level: intermediate

We use could have to make guesses about the past:

It's ten o'clock. They could have arrived by now.
Where are they? They could have got lost.

We use could to make general statements about the past:

It could be very cold there in winter. (= It was sometimes very cold there in winter.)
You could easily get lost in that town. (= People often got lost in that town.)

We use can't have or couldn't have to say that a past event was impossible:

They know the way here. They can't have got lost!
If Jones was at work until six, he couldn't have done the murder.

Ability

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.
They couldn't dance very well.

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]

Permission

Level: beginner

We use can to ask for permission to do something:

Can I ask a question, please?
Can we go home now?

could is more formal and polite than can:

Could I ask a question please?
Could we go home now?

We use can to give permission:

You can go home now.
You can borrow my pen if you like.

We use can to say that someone has permission to do something:

We can go out whenever we want.
Students can travel for free.

We use can't to refuse permission or say that someone does not have permission:

You can't go home yet.
Students can't travel for free.

Requests

We use could you … as a polite way of telling or asking someone to do something:

Could you take a message, please?
Could I have my bill, please?

can is less polite:

Can you take a message, please?

Offers

We use can I … to make offers:

Can I help you?
Can I do that for you?

We sometimes say I can ... or I could ... to make an offer:

I can do that for you if you like.
I could give you a lift to the station.

Suggestions

We use could to make suggestions:

We could meet at the weekend.
You could eat out tonight.

Questions and negatives

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

Can I ...?
Could I ...?
etc.
Can you ...?
Could you ...?

 

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.

can and could: possibility 1

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can and could: possibility 2

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can and could: other uses 1

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can and could: other uses 2

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Hi smit,

In this example, could doesn't work. Could is for a past ability (not present ability). Could can mean possibility in the present, but speaking English is an ability, not a possibility.

If I'm not 100% sure, I would say: She might be able to. (Might shows a lack of certainty.)

Best wishes,

Jonathan

The LearnEnglish Team

Submitted by IsabelTim_123 on Fri, 04/09/2020 - 16:44

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Hi English Team, Hope you are doing well. I have a few Qs 1. There are three possibilities: we can talk to a lawyer, we can go to the police, or we can forget all about it (How about 'could'?) 2. What shall we do? We can try asking Lucy for help (How about 'could') 3. What shall we do tomorrow? Well, we could go fishing (How about 'can') 4. This success could not have been achieved without your cooperation. (How about 'cannot have') Thanks so much.

Hello IsabelTim_123,

In 1 and 2, 'could' is also possible and I'd understand it to mean the same thing. In 3, there is nothing grammatically wrong with saying 'can', but it's not really an appropriate response to the question. The question asks for ideas and usually we use a hypothetical form like 'could' to answer such a question, not a form that speaks about ability. In 4, 'cannot have' is not correct because the sentence is speaking about an unreal past, i.e. a past condition that didn't really exist. 'cannot have' makes a statement about a real past action which we think did not occur.

All the best,

Kirk

The LearnEnglish Team

 

Submitted by Anisha00329 on Sun, 30/08/2020 - 01:55

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Children of divorced parents may have difficulty in forming stable relationships - How about Can? After having a baby, a woman may suffer from depression for several months - How about can? During the autumn, many rare birds may inhabit on the rocky northern coasts of the island. - How about can? The rash could be a symptom of something more serious - I saw this example in a grammar book. It says it means "maybe it is a symptom". But isn't it a general possibility (i.e. it sometimes happens)? In other words, could I use can or may instead? Thanks a lot English Team

Hello Anisha00329,

Yes, you could use 'can' is all three of those sentences to mean the same thing.

As for the sentences about a rash, both 'can' or 'may' are also possible here if you're speaking about a general possibility, but 'could' is also fine if, for example, you're a concerned parent looking at the rash and deciding whether to take that person to the hospital.

All the best,

Kirk

The LearnEnglish Team

Submitted by Deepak Kumar Sahu on Mon, 24/08/2020 - 07:28

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Hello there! Namastey! I have been looking for tense structures with modals. For example, we can have the following tense structures for the modal "Must" as in: 1. They must ask. (Simple) 2. They must be asking. (Progressive) 3. They must have asked. (Perfect) 4. They must have been asking. (Perfect Progressive) So, my question is do we have these structures for the modals "can", "dare", "need", "used to", "have to" and "ought to"? I will be grateful to your priceless assistance! Thank you! Deepak Kumar Teacher of English

Hello dkbc,

Those forms are possible for all full modals; verbs like need and dare are not always treated as modal verbs, and in fact are slowly transitioning to being normal verbs rather than modal verbs. Verbs like have to and ought to are, at best, semi-modals, and used to is generally described as a marginal modal.

For some modals it's hard to imagine a context in which they would be used because of the particular meaning of the verb. For example, while can have done is a possible form, it is very hard to imagine a context in which it would be used naturally.

 

Peter

The LearnEnglish Team

Submitted by Lucas_xpp on Thu, 20/08/2020 - 17:21

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Hi teachers, could you please help me? I find a number of sentences confusing: First - Failure to produce proof of identity could result in prosecution. I am confused why could is used. Are may, might, and can possible alternatives? Second - Whether the company could continue to use the services has been up in the air since the ban came into effect two weeks ago. Is 'can continue' possible? Third - Could you turn your chairs to face this way? Could "would you..." be used here? I appreciate your help teachers!

Hi Lucas_xpp,

In your first sentence, could is used to show possibility. You could replace it with may or might but not with can, which would show ability, not possibility.

 

In your second example, could is used to show past ability. You could use can here, but it would change the meaning to present ability. Given that the situation is still unresolved, can works fine here.

 

In your third example, you could use would. Both could and would can be used in this type of polite request.

 

Peter

The LearnEnglish Team

Submitted by Anisha00329 on Wed, 19/08/2020 - 04:56

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We could not pause the job losses indefinitely — it was always a question of ‘not if, but when’ This is an announcement by a company of job cuts. Why is "could" used instead of "can"? in every sense of the word means In every way in which something could be interpreted or understood. Why is "could" used instead of "can"? Thanks a lot teachers.

Hi Anisha00329,

In the first sentence, could not shows inability in the past. You might argue that the situation (cutting jobs) is a present situation, not a past one. But by using the past form could not, the speaker frames it as a past action. It may be referring to the time that the job cuts were decided (which is a time before the current announcement, i.e. a past time).

 

In the second sentence, could is used to show hypothetical possibilities, not real ones. It's not claiming that this thing actually is or can be interpreted or understood in all these ways in reality.

 

Best wishes,

Jonathan

The LearnEnglish Team

Submitted by AsahiYo20 on Tue, 18/08/2020 - 18:41

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1) This was the best room we could get at such short notice. - Would it be better to say "we were able to get"? 2) A course is an action or series of actions that you could take in order to deal with a particular situation - Would it be better to say "you can take"? 3) the question for the next six months is the extent to which those countries opposed to the world being divided can prevail - Since this refers to a future event, why is "can" used instead of "could"? Thanks a lot English Team.

Hi AsahiYo20,

I'll try to answer your questions in turn.

  1. Both could and were able to are possible in this sentence. Were able to is often used to show ability on a particular occasion (see here for more explanation and examples). But That was the best I could do (and variations) is a very common phrase too.
  2. You can use can or could, but the meaning is slightly different. Can presents 'taking action' as a realistic possibility for the listener. Could presents it as an imagined or hypothetical situation.
  3. We can use can to talk about the ability to do something at a future time. For example: I can go on holiday next month.

Does that make sense?

Best wishes,

Jonathan

The LearnEnglish Team

Submitted by Sharath.v on Sat, 15/08/2020 - 17:17

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You gave everything you can throughout. Is it a complusion that "could" should be used instead of using "can" Would be really grateful if someone responds to the query. Thank you :)

Hello Sharath.v,

It's hard to be absulutely certain without knowing the context, but I think could is necessary here because the whole sentence is in the past, as shown by the past tense verb gave.

 

Peter

The LearnEnglish Team

Submitted by Najmiii3579 on Sat, 15/08/2020 - 11:58

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1) He couldn’t be a doctor. He isn’t wearing a white coat This sentence seems to be about present impossibility. I think only "cannot" can be used to express such meaning. But why is "couldn't" used here instead? 2) It might/could be described as an act of provocation. Could I use may/can instead? Grateful if you could help.

Hello Najmiii3579,

Your first sentence looks rather odd to me. I think the normal form would be either [can't be > isn't wearing] for present meaning or [couldn't be > wasn't wearing] for past.

 

With your second sentence, it's difficult to say for sure without knowing the context and intention of the speaker. A word might be possible in theory, but change the meaning in such a way that it is highly unlikely, and we would have to describe each context in detail to explain.

If you can tell us what you want to say (i.e. what meaning you want to convey) then we'll be happy to help you to do so.

 

Peter

The LearnEnglish Team

Submitted by cms10 on Mon, 10/08/2020 - 18:19

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Sir, I have two questions. Grateful if you could help. 1st Sentence: "He has every attribute you could want and could play for any team." Could I use "may" or "can" instead of can? 2nd Sentence: "The earliest we can finish is next Friday." Could I use "can" or "may" instead?

Submitted by Peter M. on Tue, 11/08/2020 - 07:38

In reply to by cms10

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Hello cms10,

In the first sentence, both may and can are possibly alternatives to could in terms of grammar, but they change the meaning. May would tell us that the persion is allowed to play - not prohibited. Can woud be more similar to could but would make the situation more real. If we use could then the situation is hypothetical. If we use can then it suggests that he has a real possibility of playing for any team - he has offers and can choose amongst them, for example. For this reason, could is preferable in this context.

 

The meanings would be the same in the second sentence: may would describe what is allowed (by the rules, for example); can would describe what is possible and likely or realistic; could would describe what is hypothetically or theoretically possible.

 

Peter

The LearnEnglish Team

Hi Sir, Thanks so much for your reply. Regarding Sentence 2: "The earliest we can finish is next Friday." I am quite confused about why "can" can be used, as this sentence is talking about a future possibility. I have been taught that "can" cannot be used to talk about a future possibility. Instead, we should use "may" or "might" or "could". So could I say if I use "may" here, it can convey a sense of future possibility rather than what is allowed? And also, could I say if I use "could" here, it wouldn't convey a hypothetical possibility, but a future possibility? Thank you so much English Team.

Submitted by Kirk on Fri, 14/08/2020 - 14:54

In reply to by cms10

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Hello cms10,

As I see it, in this sentence, 'can' is used to speak about ability -- if I replace 'can' with 'are able to', the sentence still works. The phrase 'the earliest' somehow makes it clear that the sentence is not about a possibility, but rather is more like a prediction or even promise.

To convey the idea of a possibility you're not certain about, you could use 'may', 'might' or 'could': 'We might/could/may finish it next Friday'. Notice that it doesn't work to use the phrase 'the earliest' here.

Hope this helps.

All the best,

Kirk

The LearnEnglish Team

Submitted by PabloTT on Sat, 08/08/2020 - 01:51

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Hope you are doing well teachers! I read this sentence from a grammar book: The jury and witnesses were removed from the court so that they might not hear the arguments of the lawyers. The book says: "should not hear (BrE)" and "not hear (AmE)" could be used instead. May I ask whether I could use "could not hear" here?

Hello PabloTT,

Yes, you could use 'could not hear'.

To be honest, I think the best phrase here would be 'would not hear' because it expresses the intention of the person (presumably the judge) making the decision.

 

Peter

The LearnEnglish Team

Submitted by MarciaBT on Fri, 07/08/2020 - 15:44

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"If we offer you the post, when can you start?" Could I say "when could you start" or "when may/might you start" instead? Thanks teachers!

Hi MarciaBT,

Yes! When could you start? also works fine.

The versions with may or might are possible, but less common.

  • May often means permission, so When may you start? has a more specific meaning: 'When do you have permission to start?'. 
  • The version with might means there is more uncertainty about when the person can start. It invites the person to give a tentative answer (while the versions with can and could invite a more definite answer).

Does that make sense?

Best wishes,

Jonathan

The LearnEnglish Team

Thanks for your reply Sir. Would "could" convey an extra sense of politeness and be better than "can" here?

Hi MarciaBT,

No problem. Yes, could shows more politeness. Since a job interview is often the first time that the people have met, that's definitely the option I would choose.

Best wishes,

Jonathan

The LearnEnglish Team

Submitted by AsahiYo20 on Tue, 04/08/2020 - 18:27

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Hi teacher. Hope you are doing well! This is the first time that I have posted comments here. I find this page really useful. May I ask why "can" rather than "could" or "may" is used in the sentences below? I have a feeling that since the sentences refer to some future action, "could" or "may" would be a better choice. Please correct me if I am wrong. Thanks! 1. A compromise has to be reached between all the powerful vested interests before any restoration work in the city can take place. 2. I liaise with end-users, resellers and partners to see how we can improve our portfolio of products and services.

Hi AsahiYo20,

Can works fine in each sentence. However, the use is different in each example. The first sentence uses can to express possibility. The second uses can to express ability. This affects whether or not could can be used.

 

Even though if is not used, the first sentence is a form of conditional, expressing a condition and a dependent result. Could would make the sentences hypothetical and would require changes in the first clause:

A compromise would have to be reached between all the powerful vested interests before any restoration work in the city could take place.

[the speaker thinks the situation is unlikely]

 

In the second sentence, could would have a past meaning (past ability), and so the verb in the first clause would also need to be past:

I liaised with end-users, resellers and partners to see how we could improve our portfolio of products and services.

 

Peter

The LearnEnglish Team

Thanks for your detailed reply! But am I correct to say that those two sentences refer to express future possibility and future ability respectively? If that is the case, I am confused about why "can" is used because I have the belief that "can" should not be used to talk about future possibility (expressed by could, may, might) or future ability (expressed by will be able to).

Hello again AsahiYo20,

The first sentence does not express future possibility but rather describes the present situation. It could be an answer to a question such as 'Why isn't the restoration work being done?', for example.

 

The second sentence is also not about the future. It describes a person's job in general terms, not a particular future event. It would be an answer to a question such as 'What does your job entail?' and not 'What are you doing next week?'

 

Peter

The LearnEnglish Team

Submitted by patph0510 on Wed, 29/07/2020 - 18:23

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Hi teachers, 1. Her colleagues could not fault her dedication to the job. --> Assuming that this sentence is not talking about the past, could I change "could not fault" to "cannot fault"? 2. The doctor examined her carefully but could find nothing wrong. --> could I delete "could" in this sentence? (i.e. ...but found nothing wrong.) Thank you.
Hi patph0510, 1. 'Could' is referring to the past in this sentence. To say something is impossible in the present, we use 'can't' – but not 'couldn't' (see the first section above for some examples). So, your sentence with 'cannot fault' is the correct one for the present meaning. 2. Yes, you could. The meaning would be very similar, but with one difference: the version with 'could' includes the meaning of the doctor attempting or making effort to find the problem. The version without 'could' doesn't include that, and is focused on the end result (finding nothing wrong). Best wishes, Jonathan The LearnEnglish Team
Hi teacher, Thank you for your reply. As you said, and also according to a number of grammar books I have read, to say something is impossible in the present, we use 'can't'. But I sometimes see sentences using 'could (in a negative context)/could not' that seem to suggest impossibility in the present. Could you explain why 'could' is used in the following sentence? "Nobody could take serious issue with his endorsement of the principle that police officers must be deterred from breaking the very laws they are empowered and entrusted to uphold"

Hi brian1010,

I can't be absolutely sure without knowing the full context of the sentence. But I think it's fine to use Nobody could ... to mean impossibility in the present because it uses could – not couldn't. If we make a version of the sentence using couldn't:

  • People couldn't take serious issue with ...

It isn't equivalent in meaning. It would be understood as referring to a past ability, not a present possibility. As you've seen above, could and couldn't have nuances in their meanings and aren't exact opposites, so could with a negative subject (e.g. Nobody could) isn't the same meaning as couldn't (for the meaning of possibility, at least).
 

For other meanings, could and couldn't may be more direct opposites. The sentences below about ability do have the same meaning.

  • Yesterday, nobody could answer the question.
  • Yesterday, people couldn't answer the question.

Does that make sense?

Best wishes,

Jonathan
The LearnEnglish Team

Hi teacher, Are you referring to this section above: "We use could to show that something is possible, but not certain: They could come by car. (= Maybe they will come by car.) They could be at home. (= Maybe they are at home.)" Does that mean we cannot use "could not" to convey a negative meaning in the sentences above because only "could", not "could not", can indicate a present possibility? Should we use "may not" instead if we want to convey a negative meaning? Thank you.

Hi brian1010,

Yes, that's right. To say that those things are impossible for them to do, we can use can't or cannot, but not could not.

  • They can't come by car.
  • They can't be at home.

Using may not is possible, but the meaning is a bit different. May often indicates permission, so if we say They may not come by car, it means 'they cannot come by car because they don't have permission'. This usage of may not is also quite formal and emphatic.

Also, it might be confused with the 'not sure' meaning of may. They may not come by car (if there's no other context) would probably be understood as meaning 'I'm not sure whether they'll come by car or not', which is different from They can't come by car. So, I wouldn't recommend using may not for this meaning.

See this page for more explanation and examples about mayhttps://learnenglish.britishcouncil.org/english-grammar-reference/may-and-might

Best wishes,

Jonathan

The LearnEnglish Team

Thank you for your detailed reply. I would like to ask one more question as I just came across a sentence, which reads: "No one can say what might not happen if there were another earthquake." I notice that the writer uses "can" rather than "could". Does that mean in the sentence I referred to earlier ("Nobody could take serious issue with his endorsement of the principle..."), "can" is also an acceptable alternative?

Hello brian1010,

Yes, you could use can in your sentence. Could has a distancing effect, making the sentence more hypothetical; can makes the sentence more immediate, as if describing a real situation. The difference is really only one of nuance, however.

I think your sentence about the earthquake may have an error. The phrase '...what might not happen...' seems odd; '...what might happen...' is more likely, I think.

 

Peter

The LearnEnglish Team

Submitted by brian1010 on Tue, 23/06/2020 - 18:08

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Hi teacher, In the following two sentences, could I use "could" instead of "would"? Would there be any difference in meaning? 1. Would you lend me the car tomorrow night, Dad? 2. Would you fill in this form, please, sir? Thanks.
Hi teachers, Not sure if you have missed my question. I would appreciate it if you could give me a reply. Thanks!

Hello brian1010,

Yes, somehow we missed your question -- sorry about that!

In both sentences, some might argue that 'would' speaks more of willingness and 'could' speaks more of ability, but in most cases, both forms would be correct and mean the same thing.

All the best

Kirk

The LearnEnglish Team

Submitted by Ballou1982 on Wed, 15/04/2020 - 17:32

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Could you please tell me the difference between : I might be able to come today vs I might come today

Hello Ballou1982

The first one implies that the main thing is whether you can or cannot come today. You don't know yet if something might stop you from coming. For example, if your friend has invited you to visit him, but you think you will have to work, you could say this because if you have to work, you can't visit your friend.

The second one is less specific. It just says that perhaps you will come or perhaps you will not. It could be due to work, it could be because you don't want to, it could be anything, really, that prevents you from coming.

Hope this helps.

All the best

Kirk

The LearnEnglish Team

Submitted by GIRIKUMAR on Fri, 06/03/2020 - 17:25

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Hello teachers, I am back with a question. It is about "Later" and "Later on". The difference, though being distinct to me, can sometimes get me. I am sure u can help me with its distinction precisely. Could you tell me when to use " later" and "later on"?

Hello GIRIKUMAR,

As far as I am aware, there is no difference in meaning. Later on is a little more informal.

Later is often used as an informal way of saying goodbye, with the same meaning as See you later.

 

Peter

The LearnEnglish Team

Submitted by GIRIKUMAR on Tue, 03/03/2020 - 14:33

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Hello teachers, hope you are all doing great. In the Oxford dictionary, the meaning of the phrasal verb "mess up" has the verb 'fail' not with the preposition 'in' but 'at' when it's supposed 'in' as regards one of the examples below the first meaning concerned with the verb 'fail' in the same dictionary. The sentence goes thus, Mess up: to fail at something or do it badly. My question is, What's the difference between "fail in" and "fail at"? When should we you 'at' and 'in' with the verb 'fail'? Thank you, teachers.

Hello GIRIKUMAR,

I don't think there is a difference in meaning. Rather, there are certain typical patterns of use.

We tend to use fail in with words related to trying something: fail in your attempt, fail in your plan.

We tend to use fail at with activities: fail at the task, fail at the final test

 

I think fail on its own, or fail to [verb] are much more common forms, however.

 

Peter

The LearnEnglish Team

Submitted by GIRIKUMAR on Sat, 29/02/2020 - 00:53

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I m sorry to post this question despite being irrelevant here. I request that you answer it just like you do regularly in order not to fail us, teachers. That's the only reason why I come over here hopefully. In return, all I can do is express my gratitude in mere words like "Thank you so much". Could you tell me the differences between, " yourself, to yourself, and for yourself", teachers? I saw a phrase on YouTube that goes like, "understanding your values to yourself". Can we say it without " to". I did it myself. I did it to myself. I did it for myself. What do they mean despite looking like they mean the same? Thank you, teachers.

Hello GIRIKUMAR,

Myself can be used in several ways, as you show.

 

I did it myself (nobody else helped me) - this means that I did the task and nobody helped me; I did it alone.

 

I did it to myself (and nobody else was to blame) - this is generally used to describe unfortunate situations and it means that the speaker blames him- or herself; nobody else is responsible.

 

I did it for myself (not for you) - this is generally used to describe positive situations and it means that the speaker's motivation was their own benefit rather than the need or wish of someone else.

 

Peter

The LearnEnglish Team