又，再 and 还 all can be used to indicate “again” or repeating a previous action.
“又” is often used for past events.
我昨天又吃火锅了。(Wǒ zuótiān yòu chī huǒguōle.) I ate hot pot again yesterday.
这次考试他又是第一名。(Zhè cì kǎoshì tā yòu shì dì yī míng.) He was the first place in this exam again.
上个星期妈妈又生气了。(Shàng gè xīngqī māma yòu shēngqìle.) Mom was angry again last week.
“又” can also be used to indicate an action that will happen in the future under a certain condition. It’s often used in the patterns like “又要……了” “又是……了” and “又得……了”.
1) To make a judgement.
太阳不见了，看来又要变冷了。(Tàiyáng bújiànle, kàn lái yòu yào biàn lěng le.) The sun is gone, and it seems to be getting cold again.
你看，他又要迟到了。(Nǐ kàn, tā yòu yào chídàole.) You see, he is going to be late again.
别哭了，明天又是新的一天！(Bié kūle, míngtiān yòu shì xīn de yītiān!) Don’t cry, tomorrow is another day!
2） The action needs to be done again due to some objective reason.
昨天银行关门，事情没办成，今天又得请假去银行了。(Zuótiān yínháng guānmén, shìqíng méi bàn chéng, jīntiān yòu děi qǐngjià qù yínhángle.) Yesterday the bank was closed and things were not done. Today, I have to ask for leave to go to the bank again.
上个星期没买到那本书，这个星期又要去一趟书店了。(Shàng gè xīngqī méi mǎi dào nà běn shū, zhège xīngqī yòu yào qù yī tàng shūdiànle.) Having failed to buy the book last week, I have to go to the bookstore again this week.
Both “再” and “还” are used for future events.
1) “还” is used to express one’s determination, wish or plan.
这个比赛真有意思！明年我还会参加。(Zhège bǐsài zhēn yǒuyìsi! Míngnián wǒ hái huì cānjiā.) This game is really interesting! I will participate next year.
>> I decide
去年我去了一次中国，今年我还要去。(Qùnián wǒ qùle yīcì Zhōngguó, jīnnián wǒ hái yào qù.) I went to China once last year, and I will go again this year.
>> I plan
希望以后还可以和你一起吃饭。(Xīwàng yǐhòu hái kěyǐ hé nǐ yīqǐ chīfàn.) I hope I can have dinner with you in the future.
>> I hope
2) “还” indicates the continuation of an action or a state from the past to the present without any change.
你昨天说不会迟到，今天还是迟到了。(Nǐ zuótiān shuō bu huì chídào, jīntiān háishì chídàole.) You said you would not be late yesterday, but you are still late today.
已经很晚了，他还在公司开会。(Yǐjīng hěn wǎnle, tā hái zài gōngsī kāihuì.) It was late, and he was still in a meeting at the company.
1) “再” is often used if something needs to be done again because it was not finished or done well.
不好意思，你说什么？请再说一遍。(Bù hǎoyìsi, nǐ shuō shénme? Qǐng zàishuō yībiàn.) Excuse me, what did you say? Please say it again.
>> Maybe I didn’t hear it clearly.
我没听懂，你能再解释一下吗？(Wǒ méi tīng dǒng, nǐ néng zài jiěshì yīxià ma?) I didn’t understand, can you explain it again?
>> Because I didn’t understand it.
这个字又写错了，再写十遍。(Zhège zì yòu xiě cuòle, zài xiě shí biàn.) This word is wrong again, write it ten times again.
>> Because this character was wrong.
2) “再” indicates it is presumed that an action or a state will continue without any change.
如果你再这么做，我就要生气了。(Rúguǒ nǐ zài zhème zuò, wǒ jiù yào shēngqìle.) If you do this again, I will be angry.
你们再吵架，就别回家了。(Nǐmen zài chǎojià, jiù bié huí jiāle.) If you quarrel again, don’t go home.
Note that only “再” has negative forms.
不 + 再
Negate something that happens on a regular or habitual basis or a present or future event.
没 + 再
Negate the continuation of an action or a state or a past event.
I don’t like you anymore. / I didn’t like you anymore.
I don’t sing anymore. / I didn’t sing anymore.
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