Obligation and Necessity


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Obligation and Necessity

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Obligation and Necessity

  1. 1. Obligation and Necessity
  2. 2. Obligation and NecessityWhen you want to say that someone has anobligation to do something, or that it isnecessary for them to do it, you use ‘must’ or‘have to’.You must come to the meeting tomorrow.I enjoy parties, unless I have to make aspeech.
  3. 3. Obligation and NecessityThere is sometimes a difference between‘must’ and ‘have to’. When you are statingyour own opinion that something is anobligation or a necessity, you normally use‘must’.I must be very careful not to upset him.We must eat before we go.
  4. 4. Obligation and NecessityWhen you are giving information about whatsomeone else considers to be an obligationor a necessity, you normally use ‘have to’.They have to pay the bill by Thursday.She has to go now.
  5. 5. Obligation and NecessityNote: You normally use ‘have to’ for thingsthat happened repeatedly, especially withadverbs of frequency such as ‘often’, ‘always’and ‘regularly’.I always have to do the shopping.You often have to wait a long time for a bus.
  6. 6. Obligation and NecessityYou use ‘must not’ or ‘mustn’t’ to say that it isimportant that something is not done or doesnot happen.You must not talk about politics.They mustn’ t find out that I came here.
  7. 7. Obligation and NecessityNote: ‘must not’ does not mean the same as‘not have to’. If you ‘must not’ do something, itis important that you do not do it.If you ‘do not have to’ do something, it is notnecessary for you to do it, but you can do it ifyou want.
  8. 8. Obligation and NecessityWARNING: You only use ‘must’ for obligationand necessity in the present and the future.When you want to talk about obligation andnecessity in the past , you use ‘had to’ ratherthan ‘must’.She had to catch the six o’ clock train.I had to wear a suit.
  9. 9. Obligation and NecessityYou use ‘do’, ‘does’, or ‘did’ when you want tomake a question using ‘have to’ and ‘not haveto’.How often do you have to buy petrol for yourcar?Does he have to take so long to get ready?
  10. 10. Obligation and NecessityWARNING: You do not normally formquestions like these by putting a form of‘have’ before the subject. For example, youdo not normally say ‘How often have you tobuy petrol?’
  11. 11. Obligation and NecessityIn informal English, you can use ‘have got to’instead of ‘have to’.You’ ve just got to make sure you tell him.She’ s got to see a doctor.Have you got to go so soon?
  12. 12. Obligation and NecessityWARNING: You normally use ‘had to’ , not‘had got to’, for the past.He had to know.I had to lend him some money.
  13. 13. Obligation and NecessityYou can only use ‘have to’, not ‘must’, if youare using another modal, or if you want to usean ‘-ing’ form, a past participle, or a ‘to’-infinitive.They may have to be paid by check.She grumbled a lot about having to stayabroad.
  14. 14. Obligation and Necessity I would have had to go to London.He doesn’ t like to have to do the same jobevery day.
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