The three characters 还、又 and 再are usually confusing for those foreigners who just study Chinese because all of them are adverbs carrying the meaning of “again” in English. 还 indicates that the certain phenomenon continues to exist and the actions continue to process. It is similar to “still” like 他还不知道这件事. It also carries the meaning that further degree is added in the original situations. For instance, 今天比昨天还冷.

When it is used to show the repetition of actions, it is equal to 又and 再, which can be illustrated in the sentence 要锻炼身体，还要注意休息. Sometimes in daily talk, we use it to express something is just OK or “so so”. For instance, 他身体还行. The word 还 can indicate the actions in the past, at present or in the future.

The first level of meaning of 又is the same actions repeat and happen again and again. You can say 你怎么又来了 when you see someone again in the same place. Sometimes, it is functioned to emphasize something by stressing the manner of speaking, expressing a further level of meaning. During the period when you learn Mandarin, you may often hear people say 你又不是小孩.

If you intend to express that several conditions happen or exist at the same time, you can should use 又 like 又高又大 and 又便宜又实用. Furthermore, you should know it could be a transition like in the sentence 这个人挺面熟，一下子又想不起来他叫什么. When it is used in the rhetorical questions and negative sentences, it has the function of emphasizing like 人又不是神仙，难免会犯错误.

再means again and sometimes especially the second time like 再去一次. Students who learn Chinese in China often use is to say something will happen if something continue. We can say 再不走就晚了. Of course, it implies one action happens after another one such as 想好了再写. When placed before adjectives, it also means the degree is increased. For instance, 这道题简单得不能再简单了.