3 · Modal verbs · about 5 minutes
Must and need not: děi, bìxū and búyòng
obligation and its absence
Děi is the everyday “have to”, bìxū the firm “must” of rules — and the negative of both is búyòng.
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“New to me”: the explanation first, then practice. “Test myself”: 3 short questions – get at least two right and you go straight to the harder exercises.
Words you will need7
They appear in this topic’s examples and exercises and are new at this point on the learning path.
- 必须must; have to
- 商量to talk over; to consult
- 乘客passenger
- 请客to treat (somebody), pay for others
- 不必need not; there is no need
- 客气polite; courteous
- 取钱to withdraw money
Understand
RememberHave to is děi or bìxū; don’t have to is búyòng; mustn’t is bùnéng.
- Signal words
- 得
- 必须
- 不用
- 不必
- 一定要
The form
The patterns at a glance
Each row first says when or what the pattern is used for, then gives an example in Chinese.
negation
| have to (spoken) | 我得走了。 |
| must (a rule) | 你必须按时来。 |
| don’t have to | 你不用来。 |
| needn’t (formal) | 您不必担心。 |
| be sure to | 你一定要来。 |
| must not | 你不能来。 |
The rules one by one
The form this topic is about
得 is the spoken “have to”; it stands before the verb and is read děi.
太晚了，我得回家了。It’s late, I have to go home.
必须 is a firm “must”, the word for rules and requirements.
考试的时候必须关手机。Phones must be switched off during the exam.
“Don’t have to” is 不用 or 不必; neither 得 nor 必须 takes 不.
明天是星期天，你不用早起。Tomorrow is Sunday, so you don’t have to get up early.
“Must not” is a different idea: 不能, or 禁止 on signs.
你发烧了，不能去游泳。You’ve got a temperature — you mustn’t go swimming.
一定要 is a warm insistence: be sure to.
到了北京一定要给我打电话。Be sure to call me when you get to Beijing.
Example sentences
我明天早上六点得起床。I’ve got to get up at six tomorrow morning.
这件事你得跟你妈妈商量一下。You’ll have to talk this over with your mother.
所有的乘客必须买票。All passengers must have a ticket.
10 more example sentences
你不用带钱，我请客。You don’t need to bring money; it’s my treat.
这张表必须用中文填。This form must be filled in in Chinese.
您不必客气。There is no need to stand on ceremony.
我的护照快过期了，得去办一个新的。My passport is about to expire; I need to get a new one.
你不用等我，先吃吧。You don’t need to wait for me — go ahead and eat.
参加比赛的人必须先报名。Anyone taking part in the competition must register first.
要下雨了，我们得快点儿走。It’s about to rain; we’d better hurry.
这点儿小事，你不必放在心上。It’s a small thing — there’s no need to take it to heart.
明天的会你一定要参加。You really must come to tomorrow’s meeting.
医生说我必须戒烟。The doctor says I must give up smoking.
The trap English speakers fall into
Watch out
English builds “don’t have to” out of “have to”, so learners put 不 in front of 得. That form does not exist in speech, and in writing the same two characters read bùdé mean “may not” — the opposite of what was meant. “Don’t have to” is its own word, 不用.
Quick check
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Practise
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The full explanation
Read it all · about 1 min
得 — the character usually read de, here read děi — is spoken “have to, got to”: 我得走了, “I’ve got to go”. It is very common in conversation and rare in formal writing. Like every modal verb it goes before the main verb.
必须 is “must”: firmer, the word for rules, requirements and anything written down — 考试的时候必须关手机, “phones must be switched off during the exam”. Warm insistence is 一定要, “be sure to”: 你一定要来.
“Don’t have to” is 不用 in speech and 不必 in more formal language: 明天不用上班, “no work tomorrow”. There is no bù děi and no bù bìxū. English speakers build them anyway, because English makes “don’t have to” out of “have to”; Chinese uses a different word.
And “must not” is a third idea again: 不能in speech禁止on signs “You don’t have to come” (你不用来) and “you mustn’t come” (你不能来) are as far apart in Chinese as they are in English.
A closer look
One character, three readings
The character of 得 has two other jobs, each with its own reading. As de it links a verb to a description of how it is done: 他跑得很快, “he runs fast”. As dé it is “get, obtain”: 得到. Only before another verb, meaning “have to”, is it děi.
The position tells you which. After a verb it is de; in a word such as 得到 it is dé; as a modal verb, standing before the main verb, it is děi: 你得去, “you have to go”. The pinyin on this site always shows which one is meant.
Exceptions and special cases1
Exception
When you meet 不得不
then it means “have no choice but to” — a stronger must, not a negative.
雨太大了，我们不得不回家。The rain was so heavy that we had no choice but to go home.
Why? It is two negatives: “cannot not”. Note the reading dé, not děi.
Worth knowing1
Worth knowing
Búyòng xiè
不用谢, “no need to thank me”, is one of the everyday replies to thanks — the same “need not” as in this topic.
谢谢！——不用谢。Thanks! — No need to thank me.