‘To be able to’ is used to express
ability in all tenses and it also
substitutes ‘can’ in all the forms in
which it is not possible.
Examples:
We weren’t able to open the door
She has never been able to learn German
He had never been able to solve the problem
Next month I will be able to drive a car
‘Could’ or ‘be able to’ ?
I could speak Spanish so I was able to understand and
answer all his questions
Could to talk
about habitual or
permanent abilities
in the past
Ex: Last night I
could go out but I
didn’t want to.
Be able to to talk
about abilities in a
specific moment of
the past
Ex: I was able to
open the door in
the end
Note well
Could is always possible in the negative
form, even when we are talking about a
specific moment in the past.
Ex:
I was so tired that I couldn’t reach the top of the mountain.
=
I was so tired that I wasn’t able to reach the top of the mountain
Some more examples
Jack was an excellent tennis player. He could beat anybody. (he
had the general ability to beat anybody)
Jack and Alf had a game yesterday. Alf played very well but in the
end Jack managed/ was able to beat him.
Some more examples
The fire spread through the building quickly , the small boy could
leave the building but he didn’t because he wanted to rescue the
cat.
The fire spread through the building quickly ,but everybody was
able to /managed to escape (they were successful in leaving the
building)