Can vs. be able to

Could you tell me what the difference between can and be able to? Even very slight. Thank you.

“Can” is a modal auxiliary verb, and it can only be in the position of the first auxiliary verb in the sentence.

If another verb, such as “will”, “should”, etc., is occupying that position, then “be able to” is used instead of “can”.

I [color=darkred][can] help you.
I [color=darkred][will] [color=darkblue][be able to] help you.

The simplest explanation is that can has only two forms: can and could (past of can). for other tenses we use be able to:
I can’t sleep.
I haven’t been able to sleep all night.
Tom can come tomorrow.
Tom might be able to come tomorrow.
I can swim
I won’t be able to swim if I don’t try.
[color=red]To make it a little bit complicated:
You can say:
Some people are able to /can walk on their hands. (nearly the same meaning)
but we prefer can when we use the verbs of perception:
I can see a man coming towards us.
Can you smell it?

Well I think this much is enough for now!
happy studying

I have heard like this:

Can = used to tell about the senses.
I can see you
I can smell it.
I can read it. ( is this right ??)

Able= Associated to a specific action/task.
I am able to upload the file.
I am able to write the code.
I am able to convert the file.



Simple … OK.
Interesting … Definitely is.

How people explain English in this forum “can” be really thought provoking sometimes… or is that “make it able to be” thought provoking.

Happy Easter “belated” everyone.