The document discusses the modal verbs can and could. It explains that they are followed by the infinitive without "to", are not used with auxiliaries in questions or negatives, and are irregular verbs. Can is used for present ability or possibility while could expresses past or conditional situations. Other tenses like present perfect or past perfect use "to be able to" instead of can/could. The modal verbs can express ability, possibility, impossibility, prohibition, and be used in requests. "To be able to" can also be used formally for present or past situations.

1. MODAL VERBS 1: CAN/COULD
ABILITY AND POSSIBILITY
Intermediate

2. MODAL VERBS
(1) They are followed by the infinitive without to:
Ex.: I can dance reggaeton really well.
(2) They are not used with auxiliaries in questions or
negatives:
- We use inversion in questions:
Ex.: Can you speak English?
- We add “not” to the verb in negative sentences.
Ex.: Sorry, I can’t (cannot) speak any foreign language.
(3) They are very irregular. To express some tenses we have
to use other expressions (ex.: to be able to)

3. FORMS
• Present: CAN
Ex.: I can speak 15 languages apart from
English.
• Past: COULD
Ex.: I could sing very well when I was young.
• Conditional: COULD
• Ex.: I could help you if I you want.

4. TO EXPRESS OTHER FORMS AND TENSES
• Present perfect:
Ex.: Sorry, I haven’t been able to do the homework
lately. I’m too busy.
• Past perfect:
Ex.: Before the class, he had been able to finish the
homework.
• Future with will:
Ex.: You’ll be able to communicate in England, if you
study English.
• Infinitive: to be able to
Ex.: I’d like to be able to climb the Everest.
• Gerund: being able to
Ex.: I love being able to walk everywhere.

5. USES
• To express ability:
• Ex. I can drive a car.
• To express posibility/impossibility:
• Ex.: Sorry, I couldn’t come to class yesterday,
I was ill.
• To express prohibition:
• Ex: You can’t smoke in class.
• In requests:
• Could I borrow some money?

6. SPECIAL USES
• To be able to can also be used in the present and
past to be more formal:
Ex.: Sorry, I wasn’t able to come to class
yesterday.