必须
Reach for 必须 when you want to express strong necessity — 'must,' 'have to,' with no real flexibility. Stronger than 应该 (should) and 要 (need to). Use it for rules ('you must wear a mask'), conditions ('you must be 18 to enter'), and emphatic personal obligations ('I have to finish this tonight'). Common in instructions, signs, policy talk, and serious advice. The negation is 不必 or 无须 ('don't have to' — 不必须 is wrong) when you mean 'no need'; for 'must not,' use 不能 or 不可以.
Structure
Subject + 必须 + Verb Phrase
bì xū
How to Think About It
必须 is the firmest 'must' in modern Chinese. Picture a non-negotiable rule. It's an auxiliary verb, so it sits before the main verb like 要 or 应该. The trickiest thing is its negation: 必须 itself doesn't take 不 to mean 'must not.' To say 'don't have to,' switch to 不必 (don't need to). To say 'must not / can't,' switch to 不能 or 不可以. Treat 必须 as positive-only.
Examples
学生必须按时交作业。
Xué shēng bì xū àn shí jiāo zuò yè.
Students must hand in their homework on time.
明天的会议你必须参加。
Míng tiān de huì yì nǐ bì xū cān jiā.
You have to attend tomorrow's meeting.
想学好中文，必须每天练习。
Xiǎng xué hǎo Zhōng wén, bì xū měi tiān liàn xí.
If you want to master Chinese, you have to practice every day.
进医院必须戴口罩。
Jìn yī yuàn bì xū dài kǒu zhào.
You must wear a mask when entering the hospital.
Common Mistake
Learners say 不必须 for 'don't have to.' 必须 doesn't accept 不 in front — it's positive-only. To express 'no need,' switch to 不必 or 不用; for 'must not,' switch to 不能 or 不可以.
你不必须去。
你不必去。
Don't Confuse With
应该...
应该 means 'should' — recommended but flexible. 必须 means 'must' — no choice. Use 应该 for advice, 必须 for non-negotiable obligation.
要...
要 means 'need to / want to' — softer, often about plans or wishes. 必须 is firmer and almost always about external rules or strict necessity. 我要去 = I'm going / I want to go; 我必须去 = I have to go.
得 (děi)...
得 is the colloquial 'have to,' very common in speech. Similar force to 必须 but more conversational. 必须 sounds stiffer and works better in writing or formal contexts.
Practice
Fill in: 开车的时候，你____系安全带。
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必须
Translate to Chinese: To pass the test, you must study hard.
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想通过考试，你必须努力学习。
Arrange: 必须 / 你 / 这件事 / 自己 / 做
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这件事你必须自己做。
Use 必须 to state a rule at school, work, or home.
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在我们公司，员工必须九点之前到。
Hear It in Real Episodes
This pattern appears in 1 Fluentide episode:
Related Grammar Patterns
Acquire by listening
Hear 必须 in real Chinese, not in a textbook.
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