correct use of grammatical sources

2. ‘Can’, ‘could’ and ‘be able to’ are all used to describe ability
but there are important differences that you should be aware
of.
 Can is preferred if we are talking about a general
ability:
 Can you speak French?
 I can play the piano quite well.
Be able to’ is normally used to refer to ability in the
future:
 I won’t be able to start university until next year.
 Do you think you’ll be able to get a job when you leave
college?

3.  In positive sentences, ‘could’ and ‘be able to’ are used to
talk about general ability in the past.
 I could/was able to swim really well when I was younger.
(generally)
However, if we are talking about the ability to do
something on one particular occasion in the past, we
use ‘be able to’. Many upper-intermediate and advanced
level students get this rule wrong and use ‘could’. For
example, this is incorrect:
 The course was hard but I could pass the exam. (X)
This should be:
 The course was hard but I was able to pass the exam.
(particular occasion)

4. TIP: ‘Succeed in’ and ‘manage to’ are useful alternatives to ‘able to’ when we are
talking about the ability to do something on one particular occasion:
I managed to pass the exam … (more common)
I succeeded in passing the exam …
In negative sentences, however, ‘couldn’t’/’wasn’t able
to’ can be used to talk about inability to do something
on a particular occasion:
 I couldn’t/wasn’t able to understand my teacher in
the first lesson but now it’s OK.
After modal or auxiliary verbs (be, do, have, should,
etc) or ‘to + infinitive’ structures, ‘be able to’ is used:
 I should be able to take a holiday this year.
I think it’s important to be able to do basic first aid.

5. Questions for practice:
1) How many languages can you speak?
2) Do you think you will be able to understand this
grammar point?
3) Have you been able to study OK recently?
4) Do you think it’s important to be able to speak a
foreign language perfectly?
5) Could you do anything when you were younger that
you can’t do now?

6. Right words could be:
 Can and ‘able to’ are possible in questions 1 and 5 as
these are referring to general ability.
 ‘Able to’ is the only possible choice in 2 as it refers to
the future.
 ‘Able to’ is the only possible choice in 3 because if
follows an auxiliary verb.
 ‘Able to’ is the only possible choice in 4 because it
follows a ‘to + infinitive’ structure.