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

Structure

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"

Structure

Note that the "Object" mentioned above is usually also going to have an 一 and a measure word in front of it. You'll see that in the examples below.

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." While this doesn't sound so easy to confuse with 又, it's actually quite common for intermediate learners to misunderstand this use of 再 as meaning "again," so it's definitely worth mentioning here.

Structure

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

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 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 adds emotional coloring to events recurring in the future

又 is sometimes used to express that something that has happened before is going to happen in the immediate future. In this case, it usually appears with 要 (yào), 可以 (kěyǐ), 能 (néng), or 是 (shì). This usage often expresses exasperation or impatience with something happening yet again, but sometimes it's more neutral, or even happy.

Structure

Example

明天又要开会，真烦人。We're having ANOTHER meeting tomorrow. So annoying!
你又要辞职了？为什么？ You're going to resign again? Why?
夏天快到了，又可以吃冰淇淋了！ It's almost summer, and we can eat ice cream again!
明天又是星期一！ Tomorrow is Monday again.
如果我能瘦一些，我就又能穿我最喜欢的牛仔裤啦！ If I can slim down a bit, I can wear my favorite jeans again!

Both 再 and 又 have other uses as well

The comparisons above are the cases where 又 and 再 are most easily confused. This wiki also has other uses of both, however:

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

Structure

Examples

再 can be used to say "another"

Structure

Examples

再 can be used to say "and then"

Structure

Examples

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

Structure

Example

又 adds emotional coloring to events recurring in the future

Structure

Example

Both 再 and 又 have other uses as well

See Also

Sources and further reading

Books

Websites