The document discusses the uses of the modal verbs CAN, COULD, and BE ABLE TO. CAN is used to talk about ability, possibility, and permission in the present and future. COULD is the past form of CAN and is used to talk about general ability or possibility in the past. BE ABLE TO is used for all other tenses besides the present and can be used in the past to sound more formal. COULD and COULDN'T are used for requests and talking about specific instances of ability in the past, while CAN'T expresses certainty that something is impossible or untrue in the present.

1. CAN, COULD, BE ABLE TO
English File Upper-Intermediate 6B

2. Ability, possibility, permission
• Use CAN to talk about ability, possibility, and
permission
• CAN is a modal verb and it only has a present form
(present and future) and a past/conditional form
(COULD).
• For all other tenses and forms we use BE ABLE TO +
infinitive. You can also use it in the present and past
to sound more formal.

3. Ability, possibility, permission
• We often use Can I…? or Could I …? to make
requests. Could I …? is more polite
• Use COULD/COULDN’T to talk about general ability
or possibility in the past. You can also use was/were
able to, but it is more formal.
• For ability on one specific occasion in the past, you
can use couldn’t, but not could. Use was/were able
to or managed to instead.

4. Deduction
• We use CAN’T to say we are sure that something is
impossible/not true.
The supermarket can’t be closed – it’s only 16:00!
They can’t be back yet. They said they were coming
home on Sunday
• The opposite of CAN’T in this sense is MUST
She can’t be at work now. It’s only 7:30 (I’m sure it’s not true)
She must be at work now. It’s 9.30 (I’m sure it is true)