Why does Chinese use 再 for future repetition but 又 for past repetition?
再 points forward to repetition that has not happened yet; 又 points backward to repetition that already happened.
English again covers both past and future repetition with one word. Chinese splits this into 再 for future or hypothetical repetition and 又 for past repetition. Learners who translate again as 再 everywhere produce wrong sentences about the past. The fix is to check whether the repeated action already happened before choosing the adverb.
| Situation / Pattern | Formula | Natural | Avoid |
|---|---|---|---|
| Future repetition | Subject + 再 + Verb | 我明天再来。 | 我明天又来。 |
| Past repetition | Subject + 又 + Verb + 了 | 他昨天又来了。 | 他昨天再来了。 |
| Polite goodbye | Fixed expression 再见 | 再见！ | 又见！ |