Must is usually followed by an infinitive without ‘to': must 通常後接不帶to 的不定式: You must stop at the red light. 紅燈時必須停下。 Sometimes must is used without a following infinitive: 有時must 後面不接不定式: We will act alone if we must. 如果必須的話我們將單獨行動。
Must does not change its form, so the third person singular form does not end in ‘-s': must沒有詞形變化,因此第三人稱單數不以 -s 結尾: She must be asleep. 她一定是睡着了。
Questions are formed without ‘do': 構成疑問句時不用do: Must we wear our uniforms? 我們必須穿制服嗎? Must can be used in question tags: must可以用在附加疑問句中: We mustn't be late, must we? 我們決不能遲到,對嗎?
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用於表示不應該做某事。在會話或非正式書面語中常被縮略爲mustn’t: You mustn't use the office phone for private calls. 你決不可以用辦公室電話打私人電話。
For saying that it is not necessary to do something not have to, not need to, or needn't is used: 表示沒必要做某事時用not have to, not need to 或者needn’t: Children don't have to pay to go in. 兒童不必購票就可入内。 You don't need to take the test. 你不必參加考試。
There is no infinitive form of must, so to have to is used instead: must沒有不定式形式,因此可用to have to 替代: I didn't expect to have to do my own cleaning. 我沒有料想到還得自己打掃衛生。
There is no past tense, but had to is used for saying that something was necessary in the past: must沒有過去式,但可用had to 來表示過去某事是必要的: We had to show our passports. 我們只好出示護照。 Must have followed by a past participle can be used for saying that you believe something happened in the past: must have 後接過去分詞時可以用來表示相信某事在過去發生過: They must have missed the train. 他們一定沒趕上火車。 When indirect speech is introduced by a verb in the past tense, must can be used as a past tense: 當動詞的過去式引導間接引語時, must 可以用作過去式: She said that I must come immediately. 她說我必須馬上來。
There is no future tense, but must can be used for saying that someone should do something in the future: must沒有將來時,但是可用於表示某人將來必須做某事: You must be here at nine o'clock tomorrow morning. 你明天早上9點必須到這裏。 For saying that something will be necessary in the future will have to can be used: 要表示將來某事是必需的,可以用will have to: Graham will have to sleep on the sofa. 格雷厄姆將不得不睡在沙發上。