Grammar Rule in 30 Seconds
Use 'mustn't' to say something is strictly forbidden or against the rules.
- Use 'mustn't' + base verb (no 'to'): 'You mustn't smoke here.'
- It never changes form: 'He mustn't', 'They mustn't' are the same.
- It means 'don't do it'—it is not the same as 'don't have to'.
Overview
mustn't。这个词是 must not 的缩写形式，它在语法中被称为“情态动词的否定式”。mustn't 代表的是绝对的禁止。它就像是生活中的“红线”或“高压线”，告诉我们某件事是绝对不允许做的。无论是在地铁站看到“严禁携带易燃物品”的告示，还是在高考考场听到“考试期间不得交头接耳”的指令，这种强烈的、没有商量余地的禁止感，就是 mustn't 的核心灵魂。mustn't 至关重要。因为如果你在需要表达“没必要”的时候误用了 mustn't，对方可能会觉得你在下达一个严厉的禁令，甚至会因此产生误解。比如，你想说“你不用带伞”，结果说成了 You mustn't bring an umbrella，听起来就像是你强行命令对方不准带伞，这在社交场合会显得非常突兀。因此，理解 mustn't 的“禁止”属性，并将其与“建议”或“非必要”区分开来，是你迈向地道英语的重要一步。mustn't 的运作机制，我们首先要把它放回到英语的“情态动词”（Modal Verbs）家族中。对于习惯了中文语法的我们来说，情态动词其实是一个“好消息”，因为它们的用法在某些方面和中文非常相似，甚至比普通的英语动词更简单。he/she/it 往往要加 -s（比如 he eats），但 mustn't 永远是 mustn't。无论主语是谁，它都保持原样。这大大减轻了我们的记忆负担。I mustn't...(我千万不能...)He mustn't...(他千万不能...)They mustn't...(他们千万不能...)
mustn't 后面直接加动词的最原始形式，不需要加 to，也不需要加 -ing 或 -ed。- 正确：
You mustn't smoke. - 错误：
*You mustn't to smoke.*或*You mustn't smoking.*
mustn't 表达的是一种“道义上的必要性”。这意味着这种禁止通常来自于：- 法律或正式规章：如交通规则、学校校训。
- 权威人士的命令：如父母对孩子、医生对病人、老板对员工。
- 强烈的道德感或个人信念：比如你告诉自己“我绝对不能放弃”。
mustn't 相当于“禁止”、“不准”、“千万别”。它不仅仅是“不可以”（can't），它比 can't 听起来更正式、更具权威感，也更强调“后果很严重”。mustn't 的句子结构非常固定，就像一个万能公式：mustn't 和后面的动词形式都稳如泰山：I | mustn't | forget | I mustn't forget my keys. | 我千万不能忘记带钥匙。 |You | mustn't | park | You mustn't park here. | 你不准在这里停车。 |He | mustn't | tell | He mustn't tell anyone. | 他绝对不能告诉任何人。 |We | mustn't | waste | We mustn't waste food. | 我们绝对不能浪费食物。 |They | mustn't | enter | They mustn't enter the room. | 他们严禁进入那个房间。 |mustn't 与 must not：mustn't。但在非常正式的场合，比如法律条文、公司合同或极其严肃的警告中，我们会使用完整形式 must not。must not 听起来语气更重、更慢，有一种“我是在很认真地警告你”的感觉。mustn't 这个大招呢？以下是五个最常见的应用场景，结合了我们中国学习者的日常生活：mustn't 是最准确的词。- 在地铁上：
You mustn't eat or drink on the subway.(地铁内严禁饮食。) - 在图书馆：
Users mustn't speak loudly in the reading room.(读者不得在阅览室大声喧哗。) - 在淘宝/京东购物时：
You mustn't share your password with strangers.(你绝对不能把密码分享给陌生人。)
mustn't 来提醒对方。- 叮嘱孩子：
You mustn't play with fire.(你千万不能玩火。) - 实验室规则：
You mustn't touch the chemicals without gloves.(不戴手套严禁接触化学品。) - 驾驶提醒：
You mustn't use your phone while driving.(开车时绝对不能用手机。)
- 备考高考或考研时：
I mustn't stay up too late tonight.(我今晚千万不能熬夜太晚。) - 减肥期间：
I mustn't eat any more bubble tea this week!(这周我绝对不能再喝奶茶了！)
- 朋友圈八卦：
You mustn't tell anyone about what I just said.(你千万不能把我刚才说的话告诉任何人。) - 商业秘密：
Staff mustn't discuss the new project outside the office.(员工不得在办公室外讨论新项目。)
- 工作提醒：
We mustn't miss the deadline for this report.(我们绝对不能错过这份报告的截止日期。) - 旅行提醒：
We mustn't forget to bring our passports.(我们千万不能忘了带护照。)
mustn't 时最容易掉进以下三个“坑”：mustn't 和 don't have to (最经典的错误！)Mustn't= 禁止 (你没有选择，做了就会出事/违规)。Don't have to= 没必要 (你有选择，你可以做，也可以不做)。
- 如果你说：
You mustn't come to the party.(你不准来参加聚会。——这听起来像是在绝交。) - 如果你想说：
You don't have to come to the party.(你没必要非得来参加聚会。——这是一种体贴，意思是如果你忙就别来了。)
mustn't 后面加 tohave to 或 want to 的影响，很多同学顺手就写成了 mustn't to do。请记住，must 是情态动词，它很“高傲”，不需要 to 这个中介。- 错误：
*I mustn't to go.* - 正确：
I mustn't go.
sHe doesn't，但千万不要造出 He mustn'ts 这种词。情态动词在任何主语后面都保持“素颜”，不施粉黛。- 错误：
*She mustn'ts be late.* - 正确：
She mustn't be late.
mustn't 及其“近亲”，我们来看两个对比表。mustn't | 极强 (100%) | 绝对禁止 | You mustn't steal. (你不准偷窃。——法律禁止) |can't | 强 (80%) | 不能/不可以 | You can't park here. (你不能停这儿。——客观不允许) |shouldn't | 中等 (50%) | 不建议/不应该 | You shouldn't eat too much sugar. (你不该吃太多糖。——建议) |don't have to | 弱 (0%) | 不需要/没必要 | You don't have to pay now. (你现在不用付钱。——有选择权) |mustn't | 强调规则的严肃性和强制性。 |can't | 侧重于能力、许可或客观限制。 |shouldn't | 侧重于给对方提建议，语气较委婉。 |don't have to | 强调这件事不是必须做的，做不做随你。 |mustn't 听起来是不是太凶了？日常生活中能用吗？mustn't 语气很重。在和好朋友聊天时，如果你想表达“别这样做”，用 don't 或者 can't 会更自然。比如 Don't do that!。但在谈论规则、安全或者非常严肃的事情时，用 mustn't 是完全没问题的，它能显示出事情的严重性。mustn't 吗？mustn't 在英式英语中更常见。美国人更倾向于使用 can't (表示不允许) 或者 must not (不缩写)。比如，美国人可能会说 You can't smoke here 而不是 You mustn't smoke here。但作为学习者，你必须认识并理解 mustn't，因为在考试和正式文档中它非常频繁。mustn't 能用来表达对现在的猜测吗？（比如：他一定不在家）must 可以表示猜测（He must be at home - 他一定在家）。但在否定句中，表达“一定不”通常用 can't。He can't be at home.(他一定不在家。)He mustn't be at home.(❌ 这种用法极少见，且意思通常是“他不准在家”，这显然不合逻辑。)
mustn't 只管“禁止”，不管“猜测”。mustn't 后面不加 to？to 来不带 s，全家老小一个样。” 只要你把 must 看作是和 can, will, should 一样的高冷家族成员，你就不会加 to 了。Mustn't Conjugation (All Subjects)
| Subject | Modal | Base Verb | Example |
|---|---|---|---|
|
I
|
mustn't
|
smoke
|
I mustn't smoke.
|
|
You
|
mustn't
|
smoke
|
You mustn't smoke.
|
|
He/She/It
|
mustn't
|
smoke
|
She mustn't smoke.
|
|
We
|
mustn't
|
smoke
|
We mustn't smoke.
|
|
They
|
mustn't
|
smoke
|
They mustn't smoke.
|
Contractions
| Full Form | Contraction | Usage |
|---|---|---|
|
must not
|
mustn't
|
Very common in speech and informal writing.
|
Meanings
Used to express that an action is prohibited, forbidden, or a very bad idea according to rules, laws, or social norms.
Strict Prohibition
Official rules or laws that stop you from doing something.
“Passengers mustn't talk to the driver.”
“You mustn't park your car in front of the hospital entrance.”
Strong Advice Against
Telling someone not to do something because it is dangerous or a mistake.
“You mustn't tell Sarah about the party; it's a surprise!”
“You mustn't forget to take your passport to the airport.”
Negative Deduction (Rare)
Expressing a logical conclusion that something is likely not true (more common in British English).
“He mustn't be home yet; his car isn't in the driveway.”
“They mustn't like the food; they haven't eaten anything.”
Reference Table
| 主语 (Subject) | 否定情态动词 | 动词原形 | 使用场景 |
|---|---|---|---|
|
I
|
mustn't
|
forget
|
个人提醒
|
|
You
|
mustn't
|
share
|
安全规则
|
|
He
|
mustn't
|
enter
|
严格禁止
|
|
She
|
mustn't
|
know
|
秘密/社交
|
|
We
|
mustn't
|
be late
|
团队规则
|
|
They
|
mustn't
|
park
|
法律规定
|
|
It
|
mustn't
|
happen
|
一般性警告
|
正式程度
Personnel must not enter this restricted area. (A restricted room)
You mustn't go in there. (A restricted room)
You can't go in there. (A restricted room)
Stay out! No entry! (A restricted room)
Mustn't 的世界
规则
- 禁止吸烟 You mustn't smoke.
- 禁止停车 You mustn't park.
安全
- 危险 You mustn't touch.
Mustn't vs. Don't Have To
该用 Mustn't 吗？
它是否违反法律或规则？
它是可选的吗？
什么时候说 Mustn't
应用/科技
- • 分享密码
- • 发布剧透
- • 网络喷人
旅行
- • 忘带证件
- • 机上吸烟
- • 乱开舱门
按水平分级的例句
You mustn't swim here.
You are not allowed to swim here.
He mustn't eat chocolate.
He is not allowed to eat chocolate.
We mustn't be late.
It is important that we are not late.
You mustn't shout.
Do not shout.
You mustn't use your phone in class.
Using your phone is against the rules.
Drivers mustn't park on the grass.
Parking on the grass is forbidden.
You mustn't forget your keys again.
It's a bad idea to forget your keys.
We mustn't tell him the secret.
We are forbidden from telling him.
You mustn't drink the water; it's not potable.
The water is unsafe to drink.
Visitors mustn't feed the animals in the zoo.
Feeding animals is strictly prohibited.
You mustn't take photos inside the museum.
Photography is not permitted.
We mustn't let this opportunity pass us by.
It would be a mistake to ignore this.
One mustn't assume that all students learn the same way.
It is wrong to make that assumption.
You mustn't speak to your manager in that tone.
That way of speaking is unacceptable.
The medicine mustn't be taken on an empty stomach.
It is dangerous to take it without food.
We mustn't underestimate the complexity of the problem.
We should not think it is easier than it is.
The jury mustn't be influenced by media coverage.
It is legally required that they remain neutral.
Such behavior mustn't be tolerated in a civilized society.
Society should not allow this.
He mustn't have heard the news, or he'd be here.
It is logically likely he hasn't heard.
We mustn't lose sight of our original objectives.
We must remain focused on our goals.
The sanctity of the contract mustn't be compromised.
The contract must remain untouched.
One mustn't trifle with the emotions of others.
It is morally wrong to play with feelings.
The archives mustn't be accessed without explicit written consent.
Access is strictly controlled.
The delicate balance of the ecosystem mustn't be disturbed.
Human interference is prohibited.
容易混淆
Learners think 'mustn't' is the opposite of 'must' in terms of necessity. They use 'mustn't' when they mean 'it's not necessary'.
Both are used for advice, but 'mustn't' is a command while 'shouldn't' is a suggestion.
In many contexts they overlap, causing confusion about which one to pick.
常见错误
You mustn't to run.
You mustn't run.
He musts not go.
He mustn't go.
You don't must smoke.
You mustn't smoke.
I mustn't to forget.
I mustn't forget.
It's Sunday, so I mustn't work.
It's Sunday, so I don't have to work.
You mustn't parking here.
You mustn't park here.
Mustn't you go now?
Don't you have to go now?
Yesterday I mustn't go out.
Yesterday I wasn't allowed to go out.
You mustn't have a license to drive.
You must have a license to drive.
He mustn't be the thief; he was with me.
He can't be the thief; he was with me.
句型
You mustn't ___ in the ___.
We mustn't forget to ___.
It's a secret, so you mustn't ___.
The ___ mustn't be ___.
Real World Usage
You mustn't carry liquids over 100ml.
You mustn't tell him about the surprise party!
Employees mustn't use personal phones during shifts.
You mustn't turn right on a red light here.
Drivers mustn't open the food packaging.
Users mustn't post copyrighted content.
别掉进 'To' 的陷阱
美式 vs 英式
社交压力
Smart Tips
Use the full form 'must not' instead of the contraction 'mustn't' to sound more authoritative.
Use 'mustn't' for strong personal advice to friends.
Delete the 'to' immediately. Modal verbs are always followed by the base verb.
Ask yourself: 'Is it okay if I do this?' If the answer is NO, use 'mustn't'. If the answer is YES, use 'don't have to'.
发音
The Silent 'T'
In the word 'mustn't', the first 't' is silent. It sounds like 'MUSS-unt'.
Contraction Stress
The stress is usually on the first syllable: MUSS-nt.
Falling Intonation for Commands
You mustn't ↘ touch it.
Conveys a firm, final rule.
记住它
记忆技巧
Mustn't is a 'Must-Not'—if you do it, you're in a knot!
视觉联想
Imagine a giant red 'X' taped over your mouth or hands. That 'X' is the word 'mustn't' stopping you from doing something forbidden.
Rhyme
When the sign says 'Mustn't', don't be a fool. Follow the law and follow the rule!
Story
Little Red Riding Hood's mother said: 'You mustn't leave the path.' Red Riding Hood did leave the path, and she met the wolf. The word 'mustn't' was there to keep her safe from the wolf.
Word Web
挑战
Look around your room or office. Find 3 things you 'mustn't' do (e.g., 'I mustn't spill coffee on my laptop'). Say them out loud.
文化笔记
Mustn't is very common in the UK for rules and strong advice. It sounds natural and polite yet firm.
Americans often find 'mustn't' sounds a bit old-fashioned or very formal. They usually use 'can't' or 'shouldn't' instead.
In legal documents, 'must not' (the full form) is used to create a mandatory prohibition.
From Old English 'mōtan' (to be allowed/to have to). The negative 'not' was added later to create prohibition.
对话开场白
What are some things you mustn't do in a library?
Tell me about a strict rule at your workplace or school.
If you were a parent, what is one thing your children mustn't do?
Discuss the ethical things a doctor mustn't do.
日记主题
常见错误
Test Yourself
如果你在图书馆，哪个句子是正确的？
You ______ share your password with strangers.
Find and fix the mistake:
She mustn't to use her laptop in the exam.
Score: /3
练习题
8 exercisesWhich sentence is correct?
The museum is free. You ___ pay.
Find and fix the mistake:
You mustn't smoking in the hospital.
tell / mustn't / secret / you / the
Match: 1. No Entry, 2. No Cameras, 3. No Food
It is forbidden to park here.
'Mustn't' is the same as 'Don't have to'.
A: Can I tell John? B: No, you ___! It's a surprise.
Score: /8
Practice Bank
10 exerciseseat / mustn't / here / you
你不准在电影院用手机。
匹配含义
Students ______ cheat during tests.
在法律文件中，哪个更正式？
He mustn't drinks coffee at night.
forget / mustn't / they / ID / their
哪个场景需要用到 'mustn't'？
I ______ forget my mom's birthday!
我们绝对不能丢了钥匙。
Score: /10
常见问题 (8)
It is less common than in British English. Americans usually say `can't` or `not allowed to`. However, Americans still understand it perfectly.
No, `mustn't` has no past form. You should use `wasn't allowed to` or `couldn't`. For example: 'I wasn't allowed to go out yesterday.'
`Mustn't` is a strong rule or prohibition. `Shouldn't` is just advice. If you say `mustn't`, it means 'don't do it or there will be trouble!'
`Must not` is more formal and emphatic. You will see it on official signs or in legal contracts to make the rule sound very serious.
It is possible (e.g., 'Mustn't we tell him?'), but it sounds very old-fashioned. It's better to use 'Shouldn't we...?' or 'Don't we have to...?'
No. Like all modal verbs, it stays the same for all subjects. `I mustn't`, `she mustn't`, `they mustn't`.
It can be quite blunt. To be more polite, you might say 'I'm afraid you can't...' or 'Please don't...'
Yes, in British English, it can be used for logical deduction (e.g., 'He mustn't be at home'). But `can't` is much more common for this.
Scaffolded Practice
1
2
3
4
Mastery Progress
Needs Practice
Improving
Strong
Mastered
In Other Languages
nicht dürfen
German 'muss nicht' is NOT English 'mustn't'.
no deber / prohibido
Spanish often uses 'no puedes' (can't) where English uses 'mustn't'.
ne pas devoir / il ne faut pas
French impersonal 'il ne faut pas' is much more common than the English 'one mustn't'.
〜てはいけない (~te wa ikenai)
Japanese has different levels of politeness for prohibition that English lacks.
لا يجب (la yajib)
Arabic often uses the same phrase for 'mustn't' and 'shouldn't'.
禁止 (jìnzhǐ) / 不准 (bùzhǔn)
Chinese uses full verbs/adjectives rather than a modal auxiliary.
Learning Path
Prerequisites
Learn These First
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