Comparing "zai" and "you"

Both 再 (zài) and 又 (yòu) express the duplication of an action and can be roughly translated in English to "again". However, 再 is used to express actions that have not yet occurred (the "future again") and 又 is used for actions that have already occurred (the "past again"). They're not interchangeable.

再 is used to express repetition of an action in the future

再 is used to express something that has already happened and will happen again.

Structure

Subject + 再 + Verb + Object

Examples

• 我们 下次 再 来 这里 吧。We will come here again next time.
• 你 再 帮 我 打印 两 张，这 些 不 够。You will help me print two sheets, these aren't enough.
• 请 再 说 一次。Please say it one more time.
• 请 又 说 一次。Since it is asking about a future action, you can't use "又"

再 can be used to say "another"

Along with expressing the repetition of an action, 再 can be used to express the equivalent of the English word "another"

Structure

Subject + 再 + Verb + Object

Examples

• 我 要 再 看 一部 电影。I am going to watch another movie.
• 我 得 又 写 一篇 作文。Since it is about the future, you can't use "又"
• 你 可以 再 做 一碗 面条 吗。You can make another bowl of noodles.
• 我 要 又 吃 一块 蛋糕。Since it is about the future, you can't use "又"

再 can be used to say "and then"

再 can be used with 先 to express sequential order (ex. Do this....and then this...). In some cases, 再 can appear by itself to simply mean "and then".

Structure

Subject + (先) + Action 1 + 再 + Action 2

Examples

• 我们 先 做 作业 再 去 酒吧。First we'll do our work, then we'll go to the bar.
• 我 先 买 房子 再 结婚。First I'll buy a house, then I'll get married.
• 我们 买完 饮料 以后 再 看 电影。After we buy a drink, then we'll go to a movie.
• 我们 回家 再 讨论 好 吗？We discuss it after we go home, OK?
• 我 要 看 完 书 又 睡觉。'"又"can not be used as the action"go to bed" haven't occured yet.
• 你 先 吃饭 又 打 电话 給 父母。"又" does not sequence events.

又 is used to express repetition of an action that has already occurred in the past

又 is used in declarative sentences and describes the simple repetition of actions. This repeated action has already occurred once in the past.

Structure

Subject + 又 + Verb + 了

Example

• 你 怎么 又 给 我 打 电话，什么事？You keep calling me, what's the matter?
• 这 个 老 男人 又 来 了。This old man came again.
• 他 又 不 来 上 课 了，老师 可能 罚 他。He didn't come to class again. The teacher is probably going to punish him.
• 你 为什么 又 看 这本书? 你 已经 看过 了。Why do are you reading that book again？ You already read it.
• 昨天 他 再 喝醉 了"再" is not used for past events.
• 昨天 我 再 看 电影 了"再" is not used for past events.

又 indicates a emotional coloring or a regularity when involves the future

又 is also used to express repetition of an action in the future, 但是用于将来的事情描述时，“又”通常包含一种主观感情色彩的表达，比如：不耐烦，生气，无奈，讨厌，不满等等，有时候也会表示“高兴”等积极情感。或者是对某一规律性的事情的推测。记住，“又”要放在“要”“可以”“会”等助动词和“是”的后面。

Structure

Subject + 又 + 助动词/谓语动词 + Object

Example

• 明天 又 要 开会，真 烦 人。
• 你 又 要 辞职 了？为什么？
• 夏天 快 到 了，又 可以 吃 冰激凌 了！
• 明天 又 是 星期一！
• 如果 我 能 瘦 一 些，我 就 又 能 穿 我 最 喜欢 的 裙子 啦！

又 is used to emphasize negation

又 can be placed before a negating verb or adjective to emphasize said negation.

Structure

Subject + 又 + 不/没 + Verb + Object

Examples

• 我 又 不 吃 肉，只 吃素 。I really don't eat meat. I just eat vegetables.
• 他 又 不 要 去 酒吧 。He's definitely not going to the bar.
• 昨天 我 又 没 看 电影，我 做 作业 。I definitely didn't go to the movies last night. I did work.
• 我 再 不 要 吃 日本 菜，我 要 吃 中国 菜 。"再" cannot emphasize the negation by itself.
• 你 再 不 要 跟 他 一起 去 吃 饭。你 要 跟 我 去 。"再" cannot emphasize the negation by itself.

See also

• Sequencing with "xian" and "zai"
• Again in the future with "zai"
• Again in the past with "you"

Sources and further reading

Books

• Integrated Chinese: Level 2, Part 1 (pp. 157) →buy
• New Practical Chinese Reader 3 (新实用汉语课本3) (pp. 202) →buy
• Integrated Chinese: Level 2, Part 1 (pp. 157) →buy
• Integrated Chinese: Level 2, Part 2 (pp. 288) →buy
• New Practical Chinese Reader 3 (新实用汉语课本3) (pp. 202) →buy
• Integrated Chinese: Level 1, Part 1 (3rd ed) (pp. 258-9) →buy
• Integrated Chinese: Level 2, Part 2 (pp. 19-20) →buy

Websites

• Yale Chinese Usage Dictionary: Using 再 and 又