MODAL VERBS: OBLIGATION - Catedu

MODAL VERBS: OBLIGATION

• HAVE (GOT) TO expresses obligation imposed
by external authority or circumstances.
That boy has to practise the piano every day. (his
parents insist)
• MUST expresses an obligation that depends on
the speaker. It is used to give strong advice or an
order.
You must try to get to work on time. (I want you
to)
I must stop smoking. (I want to)

• Compare these examples:
Children must obey their parents. (the speaker
approves)
Children have to obey their parents. (the speaker
merely states the fact)
• In American English, HAVE TO is often used
instead of MUST.
I really have to stop smoking.

• To express obligation in the past, we can use
HAD TO, which is the past form of both HAVE
TO and MUST.
When I was 12 I had to go to bed at 10 o'clock
• When referring to the future, WILL HAVE TO is
also possible (not WILL MUST).
You'll have to clean your boots when you join the
army.

MUST is
common in
written rules

• MUST can be used after a past reporting verb as
if it were a past tense.
The doctor said that I must / had to stop smoking.

• MUSTN'T expresses there is an obligation not to
do something.
You mustn't be so rude.
• DON’T HAVE TO expresses there is no
obligation to do something.
Peter doesn't have/need to pay for his lunch. He
gets his meals free.

• In British English, DON’T NEED TO or
NEEDN’T are commonly used instead of DON’T
HAVE TO.
You needn’t tell Jennifer, she already knows.
You don't need to take your umbrella; it's going to
be a fine day.