The document discusses different uses of modal auxiliaries in English including: certainty with must and can't, possibility with can, could, may, might, ability with can, could, will be able to, permission with can, may, might, obligation with must, have to, prohibition with mustn't and can't, and advice with should and ought to. It provides examples of their affirmative and negative forms in the present, past and future tenses.

1. MODAL
AUXILIARIES

2. SPECULATION & DEDUCTION
 CERTAINTY
 AFFIRMATIVE: MUST
 NEGATIVE: CAN’T
 POSSIBILITY
 AFFIRMATIVE:
CAN
COULD
MAY
MIGHT
 NEGATIVE:
MAY NOT
MIGHT NOT

3. ABILITY
 PRESENT
CAN
AM / IS / ARE ABLE TO
 PAST
COULD
WAS / WERE ABLE TO
 FUTURE
WILL BE ABLE TO

4. PERMISSION
 PRESENT
CAN / CAN’T (The most informal way)
COULD
MAY / MAY NOT
MIGHT (The most formal way)
 PAST
COULD
WAS / WERE ALLOWED TO

5. OBLIGATION
 PRESENT AFFIRMATIVE
MUST
HAVE (GOT) TO
 PRESENT NEGATIVE (Lack of obligation)
DON’T / DOESN’T HAVE TO
 PAST
HAD TO
(Lack of obligation) DIDN’T HAVE TO
PROHIBITION
 MUSTN’T
 CAN’T

6. ADVICE
SHOULD / SHOULDN’T
OUGHT TO / OUGHTN’T TO

7. THE
END