This document discusses the modal verbs "must", "have to", and "mustn't" which are used to express obligation, necessity, and prohibition in English. It provides examples of how each modal verb is used in positive and negative sentences. Key points covered include: - "Must" and "have to" both express obligation, but "must" implies obligation from the speaker's perspective while "have to" often refers to an external obligation. - "Mustn't" is used to express prohibition and is the negative form of "must". - Modal verbs like "must" are always followed by the bare infinitive form of the main verb without "to".

1. MODAL VERBS (I):MODAL VERBS (I):
Must, have to, donMust, have to, don’t have to,’t have to,
mustn’tmustn’t

2. Have to, donHave to, don’’t have tot have to
(+) She has to get up at 7 every day.(+) She has to get up at 7 every day.
You have to drive on the left in the UK.You have to drive on the left in the UK.
(-) We don(-) We don’’t have to wear a uniform.t have to wear a uniform.
He doesnHe doesn’’t have to work today.t have to work today.
(?) Do we have to study this for the exam?(?) Do we have to study this for the exam?
Does he have to tidy his room?Does he have to tidy his room?

3.  UseUse have tohave to to talk aboutto talk about rulesrules andand
obligationsobligations, or to say that, or to say that
something is necessary.something is necessary.
I have to study harder if I want toI have to study harder if I want to
pass the exam.pass the exam.
Muslims have to pray 5 times a day.Muslims have to pray 5 times a day.

4. Must, mustnMust, mustn’’tt
(+)You must do your homework tonight.(+)You must do your homework tonight.
She must wash the dishes before sheShe must wash the dishes before she
leaves.leaves.
(-) You mustn(-) You mustn’’t smoke in class.t smoke in class.
They mustnThey mustn’’t leave their bags here.t leave their bags here.
(mustn(mustn’’t = must not)t = must not)

5.  UseUse must + infinitivemust + infinitive to talk aboutto talk about
rules and obligations.rules and obligations.
 MustMust is a modal verb. The onlyis a modal verb. The only
forms areforms are mustmust andand mustnmustn’t.’t.
 MustMust, as, as ALL MODALSALL MODALS, is ALWAYS, is ALWAYS
followed by infinitivefollowed by infinitive WITHOUTWITHOUT
TO!!!TO!!!

6. Must vs. Have toMust vs. Have to
 Both indicate obligation, but thereBoth indicate obligation, but there’s a little’s a little
difference.difference.
ItIt’s getting late. I’s getting late. I mustmust go nowgo now 
obligation from theobligation from the speakerspeaker..
ItIt’s getting late. My mum told me I’s getting late. My mum told me I havehave
toto be at home at 9.be at home at 9.  obligation fromobligation from
another personanother person..

7. OBLIGATIONOBLIGATION
FROM THE SPEAKERFROM THE SPEAKER FROM ANOTHERFROM ANOTHER
PERSONPERSON
II mustmust go to bed. Igo to bed. I’m’m
exhausted.exhausted.
II mustmust remember toremember to
phone her tomorrowphone her tomorrow
– it– it’s her birthday.’s her birthday.
YouYou have tohave to wear awear a
seatbelt in the car.seatbelt in the car.
Do youDo you have tohave to workwork
on Saturdays?on Saturdays?
II had tohad to wear awear a
uniform when I wasuniform when I was
at school.at school.

8. No obligation/necessity:No obligation/necessity:
dondon’t have to.’t have to.
YouYou dondon’t have to’t have to come to the partycome to the party
if you don’t want to.if you don’t want to.
YouYou dondon’t have to’t have to pay for thepay for the
photocopies, they are free.photocopies, they are free.

9. Prohibition:Prohibition: mustnmustn’t’t
 DonDon’t have to’t have to andand mustn’tmustn’t are completelyare completely
different. Comparedifferent. Compare
YouYou mustnmustn’t’t smoke inside a hospital. It’ssmoke inside a hospital. It’s
forbbiden.forbbiden. ((It’s the lawIt’s the law))
YouYou mustnmustn’t’t drink and drive.drink and drive.
YouYou dondon’t have to’t have to drive to the party, I’lldrive to the party, I’ll
pick you up.pick you up. (You can drive if you want,(You can drive if you want,
butbut it is not necessaryit is not necessary).).

10. Prohibition:Prohibition: mustnmustn’t’t
 DonDon’t have to’t have to andand mustn’tmustn’t are completelyare completely
different. Comparedifferent. Compare
YouYou mustnmustn’t’t smoke inside a hospital. It’ssmoke inside a hospital. It’s
forbbiden.forbbiden. ((It’s the lawIt’s the law))
YouYou mustnmustn’t’t drink and drive.drink and drive.
YouYou dondon’t have to’t have to drive to the party, I’lldrive to the party, I’ll
pick you up.pick you up. (You can drive if you want,(You can drive if you want,
butbut it is not necessaryit is not necessary).).