再 vs 又 (zài vs yòu): two ways to say “again”
再 (zài) marks repetition that hasn’t happened yet (future or hypothetical), while 又 (yòu) marks repetition that has already occurred (past or realized). In positive commands and polite requests, 再 is used; in negative commands (prohibitions), 又 appears as 别又 to warn against repeating an action. For negated past repetition, use 没再, not 没又.
Both 再 (zài) and 又 (yòu) translate to “again”, but they differ in temporal perspective. 再 is used when the repeated action is not yet realized — it lies in the future, is hypothetical, or is a plan or request. 又 is used when the repetition has already happened — the action is completed and known to have occurred. A key exception is negative commands (prohibitions), where 别又 (bié yòu) is common (e.g., 别又迟到 “don’t be late again”), while positive commands use 再. For negating past repetition, use 没再 (e.g., 他没再迟到 “he wasn’t late again”), never 没又.
When to use each
Use 再 when the repeated action has not yet occurred: future plans, promises, polite requests, or hypothetical situations. Also used in imperative sentences (positive commands). After 没, 再 negates past repetition (e.g., 没再 + verb).
再 can also indicate “then” or “after that” in sequential actions (e.g., 先吃饭再工作 “eat first then work”).
Use 又 when the repeated action is already completed or known to have happened. Common in past events, habitual actions that have occurred again, or with 了 to mark completion. Also used in negative commands with 别 (bié) to warn against repeating an undesirable action (e.g., 别又迟到).
又 often carries a tone of reproach, regret, or emphasis on the repetition being unexpected or contrary to expectation.
At a glance
| 再 | 又 | |
|---|---|---|
| Time of repetition | Future/unrealized (not yet happened) | Past/realized (already happened) |
| Positive command | Used (e.g., 再来一杯 “have another drink”) | Not used (use 再 instead) |
| Negative command | Not used (use 别又 instead) | Used (别又迟到 “don’t be late again”) |
| Negation of past repetition | Used after 没 (e.g., 没再迟到 “didn’t be late again”) | Not used after 没 (没又 is ungrammatical) |
| Typical particle partner | Often standalone or with 了 in future contexts | Often with 了 to mark completion (又...了) |
Examples
- 再明天再吃吧。Míng tiān zài chī ba.I'll eat again tomorrow.Describes a future repetition; 又 would be wrong here.
- 又昨天他又迟到了。Zuó tiān tā yòu chí dào le.Yesterday he was late again.Describes a past realized repetition; 再 would be wrong.
- 再请再说一遍。Qǐng zài shuō yí biàn.Please say it again.Polite request (future repetition).
- 又别又忘了带钥匙！Bié yòu wàng le dài yào shi!Don't forget the keys again!Negative command (prohibition); uses 别又, not 别再.
- 再他后来没再迟到。Tā hòu lái méi zài chí dào.He didn't be late again after that.Negation of past repetition; 没又 is incorrect, this is 没再.
- 又他又来了。Tā yòu lái le.He came again (as expected/again!).Past repetition with 了; often carries a tone of annoyance or just stating fact.
Common mistakes
- Using 再 for a past repetition: ✗ 昨天我再迟到了 → use 又.
- Using 又 for a future plan: ✗ 明天我又去 → use 再.
- Using 没又 as negation of past repetition: ✗ 他没又迟到 → use 没再.
- Using 别再 in a positive command (it is rare; 再 alone is normal): but note that 别再 is used in certain persuasive contexts, but the standard positive command is just 再. Avoid overcomplicating.
FAQ
- When do I use 再 vs 又 for 'again'?
- Use 再 when the action hasn't happened yet (future, plan, request). Use 又 when the action has already happened (past, realized). For example, '明天再吃' (I'll eat again tomorrow) vs '昨天又吃了' (I ate again yesterday).
- How do I say 'don't do something again'?
- Use 别又 + verb, not 别再. Example: 别又迟到 (Don't be late again). The 又 here emphasizes that the action is a recurrence of a past behavior. For a neutral 'don't do it again' (not referring to past repetition), you can also use 别再, but 别又 is more common for warning about a repeated mistake.
- How do I negate a past repetition? For example, 'He didn't come again'.
- Use 没再 + verb. Example: 他没再来 (He didn't come again). Never use 没又 — that is ungrammatical. 再 after 没 simply indicates that the repetition did not occur.
- Can 又 be used for future repetitions?
- In standard Mandarin, 又 is only used for past or realized repetitions. However, in some rhetorical or fixed expressions, 又 can appear in future contexts to express certainty or reproach (e.g., 明天他又会迟到的 'He will be late again tomorrow' — implies the speaker expects it based on past patterns). But this is still based on a past pattern, not a neutral future plan. For most learners, stick to the core rule: 再 for future, 又 for past.