diffrence between "can" and "able to"

Hi,
I know that "can" you use it juste in past or present , but "able to"
we can used in evey tense you want
ma question :
what's a difference between "can" and "able to" in a present or past sentence

[mykwyner]

Can is a verb; its past tense is could.

Able is not a verb. It must be used with an auxilliary verb and an infinitive verb.

I am able to go.
I was able to go.
We are able to go.
We were able to go.
You are able to go.
You were able to go.
I have been able to go.
He has been able to go.

[Humble]

Hi,
I think the problem asked is semantic.
1. She can't do it.
2. She is not able to do it.
What's the difference if any?
Thanks.

[Dr. Jamshid Ibrahim]

Originally Posted by Humble

Hi,
I think the problem asked is semantic.
1. She can't do it.
2. She is not able to do it.
What's the difference if any?
Thanks.

Can refers to ability only: When I was a child I could play the piano.
be able to refers to ability + putting the ability into practice:
I was able to get out of prison

So if you make use of your ability be able to is the choice usually in the past. In the presenr "can" is more often used than be able to because using an ability always refers to a past action not a present one.

[MikeNewYork]

Originally Posted by Dr. Jamshid Ibrahim

Can refers to ability only: When I was a child I could play the piano.
be able to refers to ability + putting the ability into practice:
I was able to get out of prison

So if you make use of your ability be able to is the choice usually in the past. In the presenr "can" is more often used than be able to because using an ability always refers to a past action not a present one.

I understand your point of view, but I'm not sure I see as much difference between the forms as you do.

When I was a child, I could play the piano
When I was a child, I was able to play the piano.

I see little to no difference.

I can run a mile in 5 minutes.
I am able to run a mile in 5 minutes.

Again, little to no difference for me.

[Humble]

Hi,
Well, there certainly is a difference in some cases in the past – when talking abt actions:
1. He could get another job ( and I do not mean Subjunctive)
We do not know whether he did get it – he just had a chance or possibility.
2. He was able to get another job.
He did get it.
It only applies to the affirmative and it means managed, succeeded.
3. We were late for the bus but luckily we were able to get a taxi.

Cheers

[MikeNewYork]

Originally Posted by Humble

Hi,
Well, there certainly is a difference in some cases in the past – when talking abt actions:
1. He could get another job ( and I do not mean Subjunctive)
We do not know whether he did get it – he just had a chance or possibility.
2. He was able to get another job.
He did get it.
It only applies to the affirmative and it means managed, succeeded.
3. We were late for the bus but luckily we were able to get a taxi.

Cheers

Yes, but you are changing the meaning of "could" in the first use.

If you plug "could" into your third sentence, both guys got a taxi.

"Could" has more possible uses than "able to".

[Dr. Jamshid Ibrahim]

Originally Posted by MikeNewYork

I understand your point of view, but I'm not sure I see as much difference between the forms as you do.

When I was a child, I could play the piano
When I was a child, I was able to play the piano.

I see little to no difference.

I can run a mile in 5 minutes.
I am able to run a mile in 5 minutes.

Again, little to no difference for me.

Can, must, will are the so called defective verbs because they don't have a past participle (perfect tenses), the infinitive (future tense) or in case of must not even a past tense. This means you need substitutes to fill the gap. Unfortunately the substitutes have slightly different semantic functions.So it is a kind of compromise. Have to for instance cannot replace must semantically completely.

Can (usually its past form: could) expresses only ability but not whether the speaker has made use of that ability. You might say:
I could escape from prison. It would have been easy for me but I didn't do it. Be able to by contrast shows the speaker has already made use of his/her ability

I agree with you: can, could, must, will, would: have far more semantic components than their substitutes: be able to or have to. This is the reason why the substitutes are used as a kind of compromise since they cannot cover the full semantic field.