Expressing "again" in the future with "zai (再)" - HSK 2 Grammar
While 又 (yòu) is used for "again" in the past, 再 (zài) is used for "again" in the future. That is, 再 is used when something has happened once and it will happen again.
Used as "Again"
Remember this is the future "again."
Used as "Another" or "Some More"
The English word "another" is often avoided altogether by using 再.
Used for Continuous Action
Here 再 is similar to the English "for a while longer" or "keep [going/doing]."