This document discusses the modal verbs "can", "could", and "be able to" and their uses in expressing ability and possibility. It explains that "can" is used for present ability/possibility and "could" is the past form. It also outlines how "be able to" is used to express ability/possibility in other tenses besides present/past through constructions like "have/has been able to", "will be able to", and "be going to be able to". The document notes that "be able to" can also sometimes be used instead of "can/could" to sound more formal.

1. can, could, be able to
ability and possibility
EF Intermediate 4A

2. CAN
• CAN is a modal verb and it only has a present form, which
can also be used with future meaning, and a past form
(COULD) to mean ability or possibility
Present - CAN
I can speak three languages fluently, but I can’t speak
Chinese
I’ll get back to you when I can (future meaning)
Past – COULD
She could play the violin when she was three
They couldn’t wait because they were in a hurry
Could you open the door for me please?

3. BE ABLE TO
• To express ability or possibility in other tenses than
present/past we use BE ABLE TO + infinitive
Present perfect have/has been able to
Future
Will will be able to
Be going to am/is/are going to be able to
Infinitive to be able to
Gerund being able to

4. BE ABLE TO
Luke has been able to swim since he was three
I’d like to be able to ski
I love being able to stay in bed on Sunday morning
You’ll be able to practise your English in London

5. BE ABLE TO
• We sometimes use BE ABLE TO in the present and
past (instead of CAN/COULD), usually if we want to
be more formal
Fortunately, I am able to/can accept your invitation
My colleagues weren’t able to/couldn’t come to
yesterday’s meeting