The document provides definitions and examples of the use of modal verbs to express: 1) Advice using should, ought to, shouldn't. 2) Obligation using must, have to, need to. 3) Lack of obligation using don't/doesn't have to, need to. 4) Prohibition using mustn't. 5) Permission using can, may, be allowed to. 6) Ability using can, could, will be able to, manage to. 7) Possibility using may, might, could. 8) Certainty using must, can't.

1. ADVICE (recommendations)
• SHOULD/SHOULDN´T and OUGHT TO :
– You should go to the doctor if you feel ill.
– We ought to get ready to catch the train.
– Mike shouldn´t be so impolite to his mother.
– You shouldn´t spend so much when you go
shopping.
*ought not to

2. OBLIGATION
• MUST: the obligation comes from the speaker:
– I must do the shopping today.
Or in written rules:
-- Passengers must fasten their seatbelts.
• HAVE TO: the obligation comes from others, laws
(strong obligation):
– You have to be on time to lessons.
– Drivers have to carry their driving licence with
them.
• NEED TO: necessity:
-- You need to apply for a job if you want to work.

3. NO OBLIGATION
• DON´T/DOESN´T HAVE TO/NEED TO: it isn´t
necessary:
– You don´t have to wear a skirt (if you don´t
want to).
– Mike doesn´t have to get up at seven todat. It
´s Sunday.
– We don´t need to leave now. It´s too early.
PROHIBITION
• MUSTN´T: it isn´t permitted:
– We mustn´t smoke in hospitals or schools.

4. PERMISSION
• CAN and MAY for permission in the present:
- You can use the dictionary for the tasks.
- May I sit here, please?
• BE ALLOWED TO with all tenses:
- We weren´t allowed to have our phones
switched on.
- Mary is allowed to wear piercings at work.
- They will be allowed to use calculators in
exams.

5. ABILITY
To express ability we use different modal verbs:
• in the present CAN:
– A surgeon can transplant a human face.
• in the past COULD:
– In the 18th C. doctors could operate, but
without anaesthetic.
• in the future WILL BE ABLE TO:
– Robots will be able to operate by the 22nd C.
•MANAGE TO: something possible at a specific
time with some difficulty:
- We managed to pass all our exams.

6. DEDUCTION: POSSIBILITY
• MAY when it´s possible that something happens in
the future (there are a lot of possibilities):
– Sam may pass his driving test because he did
well during the driving lessons.
• MIGHT/COULD when something is possible but it´s
difficult to happen (few possibilities):
– Valencia CF might win the league, but it would
be miracle.
– John could join our team next season, but we
don´t know yet.

7. DEDUCTION: CERTAINTY
• MUST when we are sure that something
is true or it is happening (surely, definitely):
− You must be joking because I can´t believe
what you´re saying.
• CAN´T when we are sure that something is not
true (impossible, definitely not):
– This song can´t be yours. It´s excellent.