Expressing Obligation

MUST, HAVE TO, SHOULD

… to describe what is necessary, a rule, or something we do because other people tell us to.

For example:

“ We have to buy a ticket to see the castle”

“She has to wear a uniform at work”

The negative form, DON’T or DOESN’T HAVE TO is used to describe something UNNECESSARY.

For example:

“I don’t have to work tomorrow. There’s a holiday”

… to describe something we personally think is necessary and important to do.

For example:

“You must be more careful!” “Sorry, I must go now”

…when an action is against the rules or prohibited. You can often use can’t or not allowed to instead.

For example:

“You mustn’t use a pencil to do the exam” (it is not allowed)

… to say what we think is right or correct, or is a good idea in your opinion. This is not as strong as must/ have to.

… to give advice.

For example:

“You should pay more attention”“You shouldn’t talk so much”

MUST/ MUSTN’T HAVE TO/ HAS TO DON’T HAVE TO/ DOESN’T HAVE TO SHOULD/ SHOULDN’T

They are all followed by an INFINITIVE VERB.