Listed below are some examples and uses of
"can", "could", and "be able to" in regard to ability.
can play tennis well.
She is able to speak five languages.
They can come on Friday.
Jack will be able to come next week.
Use 'can' or 'be able to' to
express an ability or possibility
NOTE: The future of 'be able to'
is 'will be able to
could swim when he was five.
"Could" in the past
general ability to do something.
were able to get tickets for
I was able to finish before 6.
I couldn't come last night, sorry.
I wasn't able to come last night, sorry.
IMPORTANT: If someone
had the capacity to do something or managed to do something on a
specific occasion in the past, we use
"was/were able to" instead of "could".
in the negative, "wasn't able to"
OR "couldn't" are both correct.