| 词组 | must |
| 释义 | must Must is usually used to say that something is necessary. It can also be used to say that you believe that something is true. Must is called a modal. See entry at ↑ The expressions have to, have got to, and need to can sometimes be used with the same meaning as must. Have got to is not used in formal English. The negative form of 'must' is must not or mustn't. The negative forms of 'have to' and 'have got to' are don't have to and haven't got to. The negative form of 'need to' is need not, needn't or don't need to. However, these negative forms do not all have the same meaning. This is explained below under negative necessity. ◊ necessity in the present Must, have to, have got to, and need to are all used to say that it is necessary that something is done. I must leave fairly soon. It must be protected at all costs. You have to find some compromise. We've got to get up early tomorrow. A number of points need to be made about this. After must you use an infinitive without 'to'. You do not use a 'to'-infinitive. If you want to say that someone is required to do something regularly, for example because it is part of their job, you use have to. You do not use 'must'. She has to do the housework while her brother reads. He has no secretarial help and has to do everything for himself. If you want to say that someone is required to do something on a particular occasion, you use have got to. I've got to report to the office. We've got to get in touch with the builders. In formal English, must is used to say that someone is required to do something by a rule or law. People who qualify must apply within six months. ◊ necessity in the past If you want to say that something was necessary in the past, you use had to. You do not use 'must'. She had to go to work immediately. We had to keep still for about four minutes. ◊ necessity in the future If you want to say that something will be necessary in the future, you use will have to. He'll have to go to the casualty department. ◊ negative necessity You use must not or mustn't to say that it is important that something is not done. You must not accept it. We mustn't forget the paraffin. If you want to say that it is not necessary that something is done, you use don't have to, haven't got to, needn't, or don't need to. I don't have to do it any longer. It's all right if you haven't got to work. You needn't put the units in every time. You don't need to go into all the details. ◊ WARNING You do not use must not, mustn't, or have not to to say that it is not necessary that something is done. If you are talking about the past and you want to say that it was not necessary for something to be done on a particular occasion, you use didn't have to or didn't need to. Fortunately, she didn't have to choose. I didn't need to say anything at all. ◊ strong belief You use must to say that you strongly believe that something is the case, because of particular facts or circumstances. There must be some mistake. Oh, you must be Sylvia's husband. Have to and have got to can also be used in this way, but not when the subject is 'you'. It has to be the explanation. Money has got to be the reason. You can use must with 'be' and an '-ing' form to say that you believe something is happening. She must be exaggerating. You must be getting old. ◊ WARNING You do not use must with an infinitive to say that you believe something is happening. You do not say, for example, 'He isn't in his office. He must work at home'. You say 'He isn't in his office. He must be working at home'. If you want to say that you believe something is not the case, you use cannot or can't. You do not use 'must' or 'have to' with 'not'. The two messages cannot both be true. You can't have forgotten me. See entry at ↑ |
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