Must is usually followed by an infinitive without ‘to': must 通常后接不带to 的不定式: You must stop at the red light. 红灯时必须停下。 Sometimes must is used without a following infinitive: 有时must 后面不接不定式: We will act alone if we must. 如果必须的话我们将单独行动。
Must does not change its form, so the third person singular form does not end in ‘-s': must没有词形变化,因此第三人称单数不以 -s 结尾: She must be asleep. 她一定是睡着了。
Questions are formed without ‘do': 构成疑问句时不用do: Must we wear our uniforms? 我们必须穿制服吗? Must can be used in question tags: must可以用在附加疑问句中: We mustn't be late, must we? 我们决不能迟到,对吗?
The negative form must not is used for saying that something should not be done. This is often shortened in conversation or informal writing to mustn't: 否定形式must not用于表示不应该做某事。在会话或非正式书面语中常被缩略为mustn’t: You mustn't use the office phone for private calls. 你决不可以用办公室电话打私人电话。
For saying that it is not necessary to do something not have to, not need to, or needn't is used: 表示没必要做某事时用not have to, not need to 或者needn’t: Children don't have to pay to go in. 儿童不必购票就可入内。 You don't need to take the test. 你不必参加考试。
There is no infinitive form of must, so to have to is used instead: must没有不定式形式,因此可用to have to 替代: I didn't expect to have to do my own cleaning. 我没有料想到还得自己打扫卫生。
There is no past tense, but had to is used for saying that something was necessary in the past: must没有过去式,但可用had to 来表示过去某事是必要的: We had to show our passports. 我们只好出示护照。 Must have followed by a past participle can be used for saying that you believe something happened in the past: must have 后接过去分词时可以用来表示相信某事在过去发生过: They must have missed the train. 他们一定没赶上火车。 When indirect speech is introduced by a verb in the past tense, must can be used as a past tense: 当动词的过去式引导间接引语时, must 可以用作过去式: She said that I must come immediately. 她说我必须马上来。
There is no future tense, but must can be used for saying that someone should do something in the future: must没有将来时,但是可用于表示某人将来必须做某事: You must be here at nine o'clock tomorrow morning. 你明天早上9点必须到这里。 For saying that something will be necessary in the future will have to can be used: 要表示将来某事是必需的,可以用will have to: Graham will have to sleep on the sofa. 格雷厄姆将不得不睡在沙发上。