再 vs 又: Two Mandarin Words for 'Again' (and Which One Needs 了)

"另一杯,谢谢" gets you a blank look. The word you want is 再: 再来一杯 (zài lái yì bēi), "another cup, please." But say "he's late again" and 再 is suddenly wrong: that one needs 又, as in 他又迟到了 (tā yòu chídào le). English gives you one word for "again" and lets you fire it anywhere. Mandarin makes you check a clock first.

The good news is the clock only has two settings. 再 is for the repeat that hasn't happened yet. 又 is for the repeat that already did. Get that straight and there's a one-second tell, sitting right there in the sentence, that confirms you picked the right one every time.

The split is timeline, not vocabulary

再 (zài) points forward. It's the "again" of things you're planning, asking for, or promising. 请再说一遍 (qǐng zài shuō yí biàn), "please say it once more." 明天再来 (míngtiān zài lái), "come again tomorrow." 再来一杯, "another round." Even the goodbye everyone learns on day one is built from it: 再见 (zàijiàn) is literally "again-see," 见 being the verb "to see." You're not saying farewell. You're saying next time.

又 (yòu) points backward. It's the "again" of things that already happened, often with a small sigh attached. 又下雨了 (yòu xià yǔ le), "it's raining again." 我又忘了 (wǒ yòu wàng le), "I forgot again." 我们队又赢了 (wǒmen duì yòu yíng le), "our team won again." The repeat is done, on the record, in the past. AllSetLearning's grammar wiki files 又 squarely under "again, in the past," and 再 under "again, in the future."

So the question is never "which word means again." Both do. The question is whether the repeat is on the calendar or in the rearview mirror.

You already learned this rule: it's 不 vs 没 again

If you've spent any time with 不 and 没, this split should feel familiar, because it's the same one. 没 negates things that didn't happen (completed, realized). 不 handles states and things that aren't yet settled. Mandarin keeps drawing the same line over and over: already-real on one side, not-yet on the other. Linguists call it realis versus irrealis. You don't need the term. You need the instinct.

Here's how to borrow it. When you reach for "again," ask the exact same question you'd ask before picking 没 or 不: has this already happened? If yes, you're in 没 territory, and the matching "again" is 又. If it hasn't happened yet, you're in 不/future territory, and the "again" is 再. The wiring you already built for negation does the work.

The 了 tell that settles every doubt

When you're not sure, listen for 了. 又 almost always drags a sentence-final 了 along behind it, because it's reporting that something just recurred: 又迟到了, 又下雨了, 又忘了. 再 almost never takes one, because the repeat hasn't occurred yet, so there's nothing to report as done. The fastest self-check in the language: 又迟到了 sounds right, 再迟到了 sounds broken.

This is a heuristic, not an iron law, so don't overtrust it. 又 can skip 了 when it pairs up in a "both…and" frame (more on that below), and a few modal contexts bend it. But for the everyday "again," the 了 ride-along is reliable enough to lean on. If you've made peace with 了 as aspect rather than past tense, this clicks: 又…了 is just "the repeat completed," marked the way completed things always get marked.

The mistake that outs every beginner

我又会告诉你 is the sentence I hear from learners who haven't sorted this out, when they mean "I'll tell you again." They've grabbed 又 for a future repeat. The fix is 再: 我再告诉你. The mirror-image error is just as common: reaching for 再 to describe something that already happened. The wrong version, 他再迟到了 for "he was late again," is the textbook mistake, and a native ear catches it instantly. The correct sentence is 他又迟到了.

Run the 了 test on your own output. If you find yourself wanting to end a 又 sentence without 了, or wanting to slap a 了 onto a 再 sentence, one of them is probably in the wrong slot. The two errors travel together because they're the same confusion seen from opposite ends.

再 has a second job: "and then"

吃完饭再去 (chī wán fàn zài qù) doesn't mean "eat and go again." It means "eat first, then go." Here 再 isn't "again" at all — it's sequencing two future actions, marking the second one as "after that." 我先想想再决定 (wǒ xiān xiǎngxiang zài juédìng), "let me think it over first, then I'll decide." English speakers almost never see this use coming, because nothing about "again" prepares you for "then."

It's still consistent with everything above, though. Sequencing is inherently forward-looking: you do this, then that. The action hasn't happened yet, which is exactly why it's 再 and not 又. Same forward-pointing word, second job.

又…又…: "both…and…"

又便宜又好吃 (yòu piányi yòu hǎochī) is how you say a place is "cheap and tasty," with not one cup of repetition in sight. Doubled up as 又…又…, 又 stops meaning "again" and starts stacking qualities: 又累又饿 (yòu lèi yòu è), "both tired and hungry." 邻居的小孩又聪明又可爱, "the neighbor's kid is both smart and cute." One catch worth knowing: the two halves should carry the same flavor, both positive or both negative. You don't mix "cheap and ugly" into this frame; it wants matching polarity.

The 还 next door

还 (hái) is the third wheel here, and it means "still" or "also," not "again." 我还想再去一次 (wǒ hái xiǎng zài qù yí cì), "I still want to go one more time," stacks 还 (still wanting) and 再 (the not-yet repeat) in one breath. DigMandarin frames 还 as the subjective one, the word for an ongoing wish, often riding with 想 or 要. If you mean "again," it's never 还. Keep it parked next door as the "still/also" word and you won't confuse the three.

The one question to keep

Next time "again" is on the tip of your tongue in Mandarin, don't translate the word. Check the clock. Has the repeat already happened? Then it's 又, and a 了 is almost certainly coming with it: 又迟到了. Hasn't happened yet, just a plan or a request or a promise? Then it's 再, no 了 in sight: 再来一杯. Two settings, one question, and a 了 to double-check your work. That's the whole machine.