When something is right on the verge of happening — the train about to pull out, the rain about to start, dinner about to be ready — Chinese wraps the whole clause in a bracket: an adverb (要／快／就要／快要) before the verb and the particle 了 at the very end. This 了 is the change-of-state 了₂, announcing that a new situation is imminent. English marks this with a verb phrase — "be about to," "be going to (any second now)" — but Chinese does it with a frame around the clause, and the sentence-final 了 is not optional: drop it and the "about to" meaning collapses. Think of the pattern as two jaws that must both be present: 要 … 了.
The basic frame: 要…了
The default way to say "about to" is 要 + V + 了. The 要 here is not the modal "want / must"; borrowed from 要 (want/will/must), it has bleached into a pure imminence marker, and the closing 了 signals that the change is right around the corner.
快点儿，火车要开了！
kuài diǎnr, huǒchē yào kāi le
Hurry up, the train's about to leave! (informal)
你看那天，要下雨了，带把伞吧。
nǐ kàn nà tiān, yào xià yǔ le, dài bǎ sǎn ba
Look at the sky — it's about to rain, take an umbrella. (informal)
孩子都快三岁了，长得真快。
háizi dōu kuài sān suì le, zhǎng de zhēn kuài
The kid's almost three already — they grow up so fast. (informal)
快(要)…了 vs 就要…了: soon vs. right away
The three intensifiers shade the "about to" differently, and one grammatical fact separates them cleanly.
快…了 / 快要…了 stresses that the event is soon — but it describes the feeling of nearness in a vague, unquantified way, so it cannot pair with a specific time word. You can't say when exactly, only "any moment now."
就要…了 means "right away / imminently," and crucially it can take a specific time expression — a clock time, a day, a date. This is the form you need for "the exam is tomorrow already."
| Frame | Nuance | Specific time word? | Example |
|---|---|---|---|
| 要…了 | about to (neutral) | usually no | 要下雨了 |
| 快…了 / 快要…了 | soon, emphatic "any moment" | ✗ not allowed | 快到了 |
| 就要…了 | imminently / already | ✓ allowed | 明天就要考试了 |
别急，我们快到了，再有五分钟就下高速。
bié jí, wǒmen kuài dào le, zài yǒu wǔ fēnzhōng jiù xià gāosù
Don't stress, we're almost there — five more minutes and we're off the motorway. (informal)
太好了，快要放假了，我都想好去哪儿玩了。
tài hǎo le, kuài yào fàngjià le, wǒ dōu xiǎng hǎo qù nǎr wán le
Yes! The holidays are almost here — I've already worked out where to go. (informal)
快点吃，电影就要开始了。
kuài diǎn chī, diànyǐng jiùyào kāishǐ le
Eat up, the movie's about to start. (informal)
Now watch what only 就要 can do — carry a specific time:
完了，明天就要考试了，我还没复习呢。
wán le, míngtiān jiùyào kǎoshì le, wǒ hái méi fùxí ne
Oh no — the exam's tomorrow already and I still haven't revised. (informal)
下星期一他们就要结婚了，请柬都发出去了。
xià xīngqīyī tāmen jiùyào jiéhūn le, qǐngjiǎn dōu fā chūqù le
They're getting married next Monday — the invitations have already gone out. (neutral)
Why English speakers stumble
English builds imminence on the verb — "the train is about to leave," "it's going to rain." Chinese builds it around the clause with a two-part frame, and the load-bearing piece is the particle at the very end, far from the verb. Learners who think tense-first keep forgetting the 了 because English puts everything up front in "about to." Retrain the instinct: whenever you say 要／快／就要 for imminence, your sentence is not finished until 了 lands.
Common Mistakes
1. Dropping the final 了. Without it, 要 reverts to "want / will" and the "about to" reading is gone.
❌ 快走，火车要开！
Wrong — without 了 this reads like 'the train wants to leave'; imminence needs the closing 了.
✅ 快走，火车要开了！
kuài zǒu, huǒchē yào kāi le
Let's go, the train's about to leave! — the sentence-final 了 completes the frame.
2. Attaching a specific time to 快要…了. Clock times and dates belong with 就要…了, not 快要…了.
❌ 明天快要考试了。
Wrong — 快要…了 can't take a set time like 明天; use 就要…了.
✅ 明天就要考试了。
míngtiān jiùyào kǎoshì le
The exam is tomorrow already. — 就要…了 accepts the specific time 明天.
3. Mis-placing the adverb after the verb. 快／要／就要 sit before the verb, like all Chinese adverbs.
❌ 我们到快了。
Wrong word order — the adverb 快 must precede the verb.
✅ 我们快到了。
wǒmen kuài dào le
We're almost there. — 快 comes before 到.
4. Using bare V + 了 for "about to." V + 了 alone marks a change that has already happened, not one that's imminent.
❌ 天黑了。
Wrong if you mean 'it's about to get dark' — 天黑了 says it has already gotten dark; add 快 for imminence.
✅ 天快黑了，我们回家吧。
tiān kuài hēi le, wǒmen huí jiā ba
It's about to get dark — let's head home. — 快…了 makes the change imminent, not completed.
Key Takeaways
- Say "about to" by bracketing the clause: 要／快／就要／快要 + V + 了.
- The sentence-final 了 is obligatory — it's the change-of-state 了 marking the imminent shift; without it the construction falls apart.
- 快要…了 stresses "any moment now" and cannot take a specific time; 就要…了 can pair with a set time (明天就要考试了).
- This is not a verb tense — it's a frame around the whole clause, so the crucial particle lands at the very end.
- Bare V + 了 means a change already happened (天黑了 = it has gotten dark); reserve it for completed, not imminent, change.
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- Sentence-Final 了 (le₂): Change of State / 'Now'HSK 1 — Sentence-final 了 (le₂) reports a NEW situation — 'now it's different': 下雨了 (it's started raining), 我懂了 (now I get it), 十二点了 (it's twelve now). It marks a change of state, not the completion of a verb.
- 要 (yào): Want, Will, MustHSK 1 — 要 (yào) spans three ideas: want (我要一杯茶), imminent or intended future (我要走了 / 我明天要去), and obligation (你要小心). Its negation splits — 不要 is 'don't!', 不想 is 'don't want to'.
- All the Aspect Markers: A Decision MapHSK 4 — A single decision map for every Mandarin aspect marker — 了, 过, 着, 在/正在, 要…了, 起来, 下去, 惯 — chosen by the shape of the event rather than by tense.