This document discusses rules for expressing obligations and permissions using modal verbs like "have to", "can", "must", and "mustn't" followed by an infinitive verb. It explains that "have to" becomes "has to" with third-person subjects like "he", "she", or "it". Examples are provided to illustrate the correct usage of these modal verbs in affirmative, negative, and question forms. Key points covered include using "don't/doesn't have to" to express lack of obligation and "can/can't" to express permission or prohibition. The document concludes by noting that "must" expresses strong obligation while "mustn't" indicates strong prohibition.

1. EXPRESSING RULES
Have to, Don’t /Doesn’t have to,
Can /Can´t /Cannot,
Must, Mustn’t.

2. Expressing rulesExpressing rules
have to, don’t / doesn’t have to, can, can’t,
must, and mustn’t are always folowed by an
infinitive verb without “to”, except “have to”.
For example:
- I have to study today. I don’t have to study
today.
- I can watch the TV tonight. I can’t watch the
TV tonight. (I can to watch the TV tonight)
- I mustn’t talk in class. ( I mustn’t to talk in class)

3. Características de los Verbos ModalesCaracterísticas de los Verbos Modales
“have to” becomes “has to” with he, she, or it.
For example:
- She has to study today.
- Marita has to visit Judith on Saturday.
- Bruno has to play soccer next time.
- The project has to be excellent.
- Our uniform has to be neat and tidy.

4. Have to
• We use Have to to express an obligation. It
refers to actions that are necessary.
- I have to take a bus to go to school.
(It´s necessary to take a bus to get to school)
• Don’t / Doesn’t have to expresses absence of
obligation, something that is not necessary to
do.
- We don’t have to go to school tomorrow.
(It´s not necessary to go to school tomorrow)

5. Have to (Affirmative)
I
You have to study.
He
She has to study.
It
We
You have to study.
They

6. Have to (Negative)
COMPLETE FORM CONTRACTED FORM
I
You do not have to / don’t have to study.
He
She does not have to / doesn’t have to study.
It
We
You do not have to / don’t have to study.
They

7. Have to (Questions)
Do/ Does + Subject + have to + vº infinitive + C + ?
Do I have to study English ?
you
he
Does she have to study English ?
it
we
Do you have to study English ?
they

8. Have to (Questions)
If there is a Question Word (Wh-) in the interrogative
sentence, it goes at the beginning of th esentence.
For example:
Wh- + Do/ Does + Subject + have to + vº infinitive + C + ?
Why does she have to study English?

9. Have to (Short Answers)
AFFIRMATIVE
Yes, + subject + do/does
Yes, I do.
you
he
Yes, she does.
it
we
Yes, you do.
they
NEGATIVE
No, +subject +don’t /doesn’t
No, I don’t
you
he
No, she doesn’t
it
we
No, you don’t
they

10. CAN & CAN’T = CANNOT
1. We use can / can’t / cannot + vº infinitive to
express permission.
- I can play in the playground.
- I can’t / cannot eat in class.
- We can´t write on the tables.
- The school van can´t be late for school.

11. MUSTN’T
• We use Must to express strong obligation
and duty.
• Mustn’t expresses strong prohibition.
We must respect the Angelus prayer.
- You mustn’t insult your classmates.