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MUST - HAVE TO - NEED 1-Necessity (obligation) When it is necessary to do something, To get a cheap ticket,you must / have to book in advance. You must be here by 8 o’clock at the latest. Before you purchase a house,you must / have to / need to consider all the costs. Note : have got to is informal and used particularly in spoken English MUST has no other forms than the present tense ( must can only be used to refer to present or future obligation.) To talk about the past (which was necessary to do something) we use had to instead;
The car broke down and we had to get a taxi I had to leave early because I wasn’t feeling well.. Have to suggests that someone else or some outside authority or circumstances makes it necessary. Must is prefered when the speaker decides it is necessary and to express urgency with you and in public notices. I have to see the headmaster (..she has called me to her office) I must see the headmaster (...I want to discuss something with her) I have to work from 9:00 am till 5:00 pm. I have to pay my road tax soon. You must start working harder! (I say so) You have to turn left here.(It is the law.)
Negative forms of the must - have to - need to Mustn’t Mustn’t Not allowed; being forbidden Life belts mustn’t be removed. You mustn’t leave the room befpre the end of the exam. You mustn’t walk on the grass here. You mustn’t put anything on the shelves until the glue has set hard.
Don’t have to needn’t don’t need to Not necessary; no obligation You don’t have to work such long hours.You won’t earn any more we needn’t go into the details now, but we seem to agree on the general principles. You don’t need to whisper.Nobody can hear us. She doesn’t need to come with us if she wouldn’t like. Compare the sentences below. You needn’t work tomorrow if you don’t want to. You mustn’t move any of the papers on my desk.
Didn’t need to - didn’t have to - needn’t have ( past forms of the negatives) When we say that it wasn’t necessary to do something in the past and it wasn’t done;we use didn’t need to or didn’t have to..It refers to an unnecessary action which wasn’t done. When we say that we know something happened in the past although it wasn’t necessary; we use needn’t have .It refers to an unnecassay action which was done. Chris and June phoned to say that they couldn’t come to eat,so I didn’t need to cook dinner (I didn’t cook the dinner.) I needn’t have cooked dinner.Just as it was ready,Chris and June phoned to say that they couldn’t come to eat.(I did cook the dinner)
I needn’t have bought more sugar ( I did but we had enough) I didn’t need to buy more sugar. ( I didn’t ,because we had enough.) You needn’t have paid all at once. ( You did pay.) I didn’t need to go to the dentist again, luckily. 2-Logical conclusion (assumption); deduction Must can be used to say that we are sure about something (because it is logically necessary) %95 certainty. Mary must have a problem, she keeps crying. The hall is packed.there must be about 500 people at the meeting -Why is not John in class? -He must be ill. ( Usually he is in class everyday, but when I saw him last night,he wasn’t feeling good.So my best guess is that he is sick today.I can’t think of another possibility.) There is the doorbell.It must be Roger.
MUST is used with the perfect infinitive for deductions about the past. The lights have gone out.A fuse must have blown. You hadn’t eaten for hours .You must have been hungry! I took only train home.So I must have left the umbrella on the train. Paulo fell asleep in class this morning.She must have stayed up too late last night. She must have been upset when she heard the bad news. He must have played really well to beat Agassi.
Negative forms of MUST NEGATIVE FORMS of MUST can’t couldn’t A- I’m seeing Dr.Evans tomorrow. B- That can’t be right.He is on holiday then. That can’t be the postman. It is only seven o’clock.. It couldn’t be Peter.He never knocks at the door in this way. A- I’ll call Robert and ask him to give me a ride home. B- He couldn’t be at home now.He must be working.
PAST FORMS of NEGATIVE DEDUCTIONS He wasn’t there at the time.It couldn’t have been his fault. A- Jim didn’t say hello to me while he was passing by. B- He can’t have noticed you. She can’t have borrowed your bicycle as she has a broken leg. He couldn’t have arrived home shortly after he left the office because there was a running race on the bridge and most of the roads were blocked.