ask again go to there again come to here again say again

Generally, 再 refers to some usages, 1, 再 refers to do something one more time or some more if the act has been finished, and once can be omitted sometimes. E.g. 再唱一首歌=Sing one more song! 我明年要再去厦门=I'll go to Amoy once again next year. 2, 再 can also refer to continue doing something, if the act is not finished in the context. E.g. 我想再多看一阵电视= I want to watch TV for a more while. 他还要再睡一会儿=He wants to continue his sleep for a little longer. 3, 再 implies a tone with uncertainty, the common phrases are 再看，再说，再等等 To be added。。。

再 = again. 再 is usually followed by something like 一次，两次，etc. 再说一次 = Say it one more time.