吗，呢 and 吧 are all modal particles used at the end of interrogative sentences.
A declarative sentence can be changed into a yes-no question by adding the question particle “吗” at the end of it. Wh-question or alternative question can’t use 吗.
你很忙吗？（Nǐ hěnmáng ma?）Are you busy?
他喝水吗？（Tā hē shuǐ ma?）Does he drink water?
✘ 谁很忙吗？who is very busy?
✘ 你忙不忙吗？Are you busy?
Note that 吗 is used when the speaker is pretty sure about the answer.
√ 你是中国人吗？(Nǐ shì Zhōngguó rén ma?) Are you Chinese?
✘ 你可能是中国人吗？ Are you maybe a Chinese?
– 呢as an interrogative particle, is used after a noun or pronoun, forming a question about the situation mentioned previously. “A……, B + 呢?”
A: 你好吗？(Nǐ hǎo ma?) How are you?
B: 我很好，你呢？（Wǒ hěn hǎo, nǐ ne?）I`m very good, how about you?
– When using at the end of a sentence, the interrogative particle “呢” asks about the location of somebody or something.
我的书呢？ (Wǒ de shū ne?) Where is my book?
她在哪儿呢？ (Tā zài nǎr ne?) Where is she?
– 呢 indicates that the speaker does not know the answer or is uncertain about the answer. It can only be used in Wh-question and alternative questions.
哪个人更聪明呢？(Nǎge rén gèng cōngmíng ne?) Which person is smarter?
>> The speaker is uncertain or doesn’t know.
我们去北京还是去上海呢？(Wǒmen qù Běijīng háishì qù Shànghǎi ne?) Should we go to Beijing or Shanghai?
>> Consultation tone.
– 呢 is used at the end of a declarative sentence or after a sentence with an adjectival or verbal predicate to confirm a fact and convince someone in an exaggerative mood.
别急，现在时间还早呢。(Bié jí, xiànzài shíjiān hái zǎo ne.) Don’t worry, it’s still early now.
学校离我们家要一个小时呢！(Xuéxiào lí wǒmen jiā yào yīgè xiǎoshí ne!) The school is an hour away from our home!
– 吧 is used to ask about uncertain things by guess.
这辆车很贵吧? (Zhè liànɡ chē hěn ɡuì bɑ?) This car is expensive, right?
你们认识吧? (Nǐmen rènshi bɑ?) You know each other, right?
– 吧 is used to indicate persuasion, suggestion or request at the end of an imperative sentence with a softened mood.
你快去开会吧。(Nǐ kuài qù kāihuì bɑ.) Hurry, just go to the meeting.
你昨天太累了，今天就在家休息吧。(Nǐ zuótiān tài lèi le, jīntiān jiù zài jiā xiūxi bɑ.) You were too tired yesterday. Rest at home today.
请你帮我一下吧。(Qǐnɡ nǐ bānɡ wǒ yí xià bɑ.) Please help me.
– 吧 is used to indicate agreement or permission.
A: 这样写可以吗？(Zhèyànɡ xiě kěyǐ mɑ?) Is it okay to write like this?
B: 可以，就这样吧。(Kěyǐ, jiù zhèyànɡ bɑ.) Yes, that’s it.
A: 我可以坐这里吗？(Wǒ Kěyǐ zuò zhèlǐ mɑ?) Can I sit here?
B: 你坐吧。(Nǐ zuò bɑ.) Sit down.
– When using 吗, the speaker does not know the answer. When the speaker may know the answer and wants to get confirmation, 吧 is used.
你是老师吗？(Nǐ shì lǎoshī ma?) Are you a teacher?
>> Maybe you are a teacher, maybe not.
你是老师吧？(Nǐ shì lǎoshī ma?) Are you a teacher?>>I think you may be a teacher.
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