Grammar RevisionHave to, must, mustn’t, need, should, may, might
Obligation and necessity: must, have toWe use must when the authority comes from the speaker You must be home by 10 o’clock I’ve got a pain in my back. I must go and see the doctor.We use have to when the authority comes from outside the speaker I have to be home by 10 o’clock. (My parents insist)
Obligation and necessity: must, have to• Must: for present and future (the rest of tenses with have to I had to work late yesterday I must work late tomorrow He hates having to get up early She’s had to work hard all her life Did you have to walk home last night?
Obligation and necessity: must, have toUse must and: drink, take, stay and continueDoctor: Well,Mrs. Woods, your temperature is a little high, so you … in bed. You can eat whatever you like, but you …plenty of liquids. And I’ll give you some medicine. You …it three times a day after meals. And you …to take it for the next ten days.
Obligation and necessity: must, have to• Use: have to and drink take and continue.• Mrs Woods: The doctor gave me some medicine. …it three times a day after meals. And I …to take it for the next ten days. I’m not allowed to get up at the moment. I …in bed for the next few days. Oh, and I’m allowed to eat whatever I like, but I …plenty of liquids.
Obligation and necessity:mustn’t, don’t have to, don’t need to• We use mustn’t when there is an obligation not to do something• We use don’t have to when it is not necessary to do something. We can also use don’t need to, or needn’t
Possibility: may, might, could-to talk about present or future possibility.+++may ++might +could“There’s someone at the door”. It may be Sarah. (=Perhaps it is Sarah)“We aren’t sure what we are going to do tomorrow. We might go to the beach. (Perhaps we will go to the beach)“Where’s Simon?” “He could be in the living room”. (Perhaps he is in the living room)
Obligation and advice: should, ought to• to talk about obligation and duty, to ask for and give advice, and, in general, to say what is right or good.• You should learn to swim/You ought to learn to swim• You shouldn’t tell lies/You oughtn’t to tell lies• Ought to: to talk about authority which comes from outside the speaker (laws, rules)• Should +inf without to• Ought to +inf http://www.youtube.com/watch? v=GqH21LEmfbQ