unable or can't

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moniki

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Hello there,
Here,
Some students are unable to use a computer or some students can't use a computer. Is there any difference in meaning between these two sentences?:-? If there is some, when should I use "can't" or "unable". Thanks a lot.:)
 

raihan89

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hello moniki...

I'm new here so my English is not that good but still i want to try.Can i ??

Actually the meaning of both words is kind of similar but it is used depend on the sentence . Usually can't is used for prohibited one's to do something right? or any informal usage..unable is more formal way and polite..
That is just my opinion hope it will help you .:-D
 

cubezero3

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Hola, amigo.

I am not a teacher. Nor am I a native speaker.

I'd like to share my understanding of the difference between can and be able to. I hope this will save teachers some time.

If you use can and be able to in present and future tenses. They basically have the same meaning, i.e. to show someone has the ability to do something.

But, there's a little difference when they're used in past tenses. In this case, we use could instead of can and was or were able to. Here could conveys the meaning that during a period of time in the past, someone had the ability to do something. At the same time, was or were able to shows in a specific past event, someone successfully did something.

An example may help clarify the difference. Let's suppose there were two men on board when the tragedy of Titanic happened. These two miserable figures were Joe Bloggs and John Smith.

Let's take a look at Joe Bloggs' case for a start. Soppose he grew up in Cormwall and started swimming when he was merely three years old. When the tragedy took place, he was 27 years old and already a very good swimmer. He'd once swimmed across the English Channel. Unfortunately, when the ship broke in to two parts, he was at the wrong side of the vessel. However hard he had tried to escape, he was finally pulled down.

When we talk about him now, we can say:

Joe Blogg could swim when the ship went down.

Joe Blogg wasn't able to swim to a lifeboat.

Now, let's consider John Smith. All his life he stayed away from water and never chose vessels as transportation, except for the Titanic, the unsinkable vessel. As he was informed that the ship was going down, he paniced at the first. Then a captain gave him a lifevest. When the ship began to break itself apart, he fell in to the sea. He was lucky for the ship had only just started to sink. Because he had a lifevest, he floated on the water. After seeing a lifeboat not far away from him, he used every bits of his body to get himself move towards it. So he did it and became one of the few suivivors.

When we talk about John Smith now, we can say:

John Smith couldn't swim when the ship went down.

John Smith was able to swim to a lifeboat.

In a word, when talking about a past event, you could do something was no guarantee that you were able to do it. It could be one of those days.

Richard
 

moniki

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Thank you very much, you have been very clear and very specific, I finally got it. I hope one day I can express myself like you did. Best wishes, Mónica.
 

e2e4

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What does

He couldn't have swum as the boat sunk.

mean?

Thanks
 

BobK

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It's a very odd sentence. "Couldn't have" in this sort of context means 'It must have been impossible...'. But 'as' suggests an ongoing action, so I'd expect a sentence like this: 'He couldn't have swum away as the ship was sinking'.

The use of the present fixes the belief about the possibility of the action in the mind of the speaker. So you can have a disagreement like this:

He can't have swum away while the ship was sinking.
Yes he can; what's more, he did.
(The word 'while' came to me more naturally; 'as' there sounds more like 'because': He can't have done it, as he was miles away.')

b
 

Koronas

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Hello there,
Here,
Some students are unable to use a computer or some students can't use a computer. Is there any difference in meaning between these two sentences?:-? If there is some, when should I use "can't" or "unable". Thanks a lot.:)

I am a native English speaker, not a teacher. Here is my view:-

"Some students are unable to use a computer" means that they do not have the ability. They do not know how.

"Some students can't use a computer" is ambiguous and might have the above meaning but it might also mean that they are not permitted to use it.
 

e2e4

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It's a very odd sentence. "Couldn't have" in this sort of context means 'It must have been impossible...'. But 'as' suggests an ongoing action, so I'd expect a sentence like this: 'He couldn't have swum away as the ship was sinking'.

The use of the present fixes the belief about the possibility of the action in the mind of the speaker. So you can have a disagreement like this:

He can't have swum away while the ship was sinking.
Yes he can; what's more, he did.
(The word 'while' came to me more naturally; 'as' there sounds more like 'because': He can't have done it, as he was miles away.')

b

I think I could also have said

He couldn't swim while the ship was sinking.

Is this correct?
 

BobK

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I think I could also have said

He couldn't swim while the ship was sinking.

Is this correct?

I added the 'away' because without it the sentence looks very odd; it suggests to me that he didn't have the necessary skill. 'Swim' on its own, preceded by can/could, refers to personal training/skill/ability. If someone can or can't swim it means that - unless there is a specific obstacle: 'you can't swim [through waves that big/against that current/ in that water - it's freezing...]'.

But 'while' is fine.

b
 

e2e4

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I am sorry that I forgot to add the away.
I've understood that away must be in the sentence.

This time, I focused my question on the couldn't swim away and not at the couldn't have swum away

Which one is correct

1. He couldn't swim away while the ship was sinking.
2. He couldn't have swum away while the ship was sinking.

Or both are correct?

Thank BobK
 
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