*OBLIGATION *PROHIBITION *ADVICE modal VERBS *OBLIGATION *PROHIBITION *ADVICE

Should/shouldn’t SHOULD/SHOULDN’T are used when we want to give a strong opinion, telling someone the best thing to do. We use SHOULD and SHOULDN’T to give and ask for advice and recommendations. We can request advice by saying “Do you think I should…?” or “Should I…?”. AFFIRMATIVE You should work hard. NEGATIVE You shouldn’t worry if you make a mistake. QUESTION Should you wear formal clothes for an interview? SHORT ANSWERS Yes, you should/No, you shouldn’t.

HAVE/HAS TO HAVE TO and HAS TO express obligation. We use HAVE TO to talk about things which are obligatory or necessary. We use DON’T HAVE TO to talk about things which are not obligatory or necessary (lack of obligation). HAVE/HAS TO and MUST mean the same when we are talking about rules and obligations. We can also say “I have got to…” and this has the same meaning. AFFIRMATIVE Police officers have to wear a uniform. NEGATIVE Teachers don’t have to wear a uniform. QUESTION Do police officers have to wear a uniform? SHORT ANSWERS Yes, they do/No, they don’t.

Don’t/doesn’t have to DON’T and DOESN’T HAVE TO = no obligation. Make it clear that this is not the same as MUSTN’T, which is used for prohibition. DON’T/DOESN’T HAVE TO, on the other hand, means it is not necessary to do something, but you can do it if you wish.

MUST/MUSTEN’T* MUST and MUSTN’T are used to express obligation or prohibition. MUST is not very common in question forms; we usually say “Do I have to…?” instead. We use MUST to talk about rules, regulations and obligations. We use MUSTN’T to talk about prohibitions. Police officers must wear a uniform. You mustn’t smoke at school.