Learner's definition of MUST
[modal verb]
1
a somewhat formal in US English —
used to say that something is required or necessary必须；不得不 -
You must stop. [=you have to stop; I command you to stop]你必须停下来。
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I told him what he must do. [=what he had to do]我告诉过他必须做哪些事。
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One must eat to live.人一定要吃东西才能活。
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You must follow the rules.你必须遵守这些规则。
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We must [=have to, need to] correct these problems soon or the project will fail.我们必须马上纠正这些问题，不然计划会失败。
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I must remember to stop at the store.我一定要记住在那家商店停一下。
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“Must you go?” [=do you have to go?] “Yes, I'm afraid I really must.”“你非得走吗？”“是，恐怕我真的得走了。”
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“Must you go?” “No, I don't have to.”“你非得走吗？”“不，我不是非走不可。”
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If you must go, at least wait until the storm is over.如果你必须走的话，那也至少等到暴风雨过去再走。
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It must be noted, however, that the company was already in financial difficulties.然而，必须指出，公司已经出现财政困难。
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We must keep/bear in mind that she didn't have any previous experience. = It must be borne in mind that she didn't have any previous experience.我们必须记住，她之前没有任何经验。
◊ Note the difference in meaning between must not and not have to.注意must not和not have to意思上的区别。
b —
used to say that something is required by a rule or law（按规则或法律）必须，务必 2
somewhat formal in US English —
used to say that someone should do something应该（做某事） -
You must [=ought to, should, have to] read this book. It's fantastic!你应该看这本书，太好看了！
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You must come visit us soon. [=we would like to have you come visit us soon]你应该快些来看我们。
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You really must see the doctor about that cough. [=I urge you to see the doctor; I really think you need to see the doctor]你确实应该找医生看看咳嗽了。
3
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used to say that something is very likely很可能，肯定 -
It must be almost dinner time.一定快到晚餐时间了。
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She must think I'm a fool.她肯定认为我是傻瓜。
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It must have been the coffee that kept me awake.肯定是喝了咖啡让我一直很清醒。
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He must have been the most gifted student at the school. [=I think he was the most gifted student]他一定是全校最有天赋的学生。
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He must have a lot of money to live the way he does.他肯定很有钱，才可以过那样的生活。
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The bus must be coming soon.公共汽车肯定马上就来了。
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You haven't eaten all day. You must be hungry.你整天都没吃东西，一定饿了吧。
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You're going to wear that? You must be joking!你打算穿那件？肯定是开玩笑吧！
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You must have been very worried.你肯定很担心了吧。
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You must be thrilled about the new baby.有了小宝宝，你肯定很兴奋吧。
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If he really was there, I must have seen him, but I don't remember seeing him.要是他真的在那儿，我肯定看到他了，但是我不记得见过他。
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There must be some mistake.一定是出错了。
4
—
used in various phrases to emphasize a statement用于各种短语，表强调 -
I must say, I was surprised to hear from him.我必须要说，收到他的信我很意外。
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She's a talented actress, I must say.我得承认，她是个有才华的女演员。
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She's a talented actress, you must admit.你得承认，她是个有才华的女演员。
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I must admit, I expected better results.我得承认，我原以为结果会比这要好。
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I must warn you, this will not be easy.我得提醒你，这并不容易。
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I must confess, I haven't actually read the book yet.我得坦白，实际上我还没看过那本书。
5
somewhat formal in US English —
used in questions that express annoyance or anger干嘛非得要，总是要（用于疑问句，表示气恼或愤怒）
if you must
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used to say that you will allow someone to do something even though you do not approve of it（表示虽不赞成但可允许）如果你非做…不可
if you must know
— see 1know 2 must /ˈmʌst/ noun
plural musts
plural musts
Learner's definition of MUST
[count]
: something that is or seems to be required or necessary必备品；必须做的事情—
usually singular通常用单数 -
If you're going to hike this trail, sturdy shoes are a must.要是你打算徒步走这条路，结实的鞋子是必备的。
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Regular exercise is a must [=is very important; is strongly recommended] as you grow older.年纪大了，经常锻炼很必要。