HSK 5 grammar · new HSK syllabus
一旦…就…: once, if ever
一旦 A 就 B = once A happens, B follows: 一旦养成习惯，就很难改.
Structure
- 一旦 + A，(subject) + 就 + B
How it works
一旦 introduces a situation that, if or once it happens, leads to a definite result: 一旦错过这次机会，就很难再有了.
It is often used for serious or lasting consequences.
Examples
-
一旦养成了坏习惯，就很难改掉。
Once you’ve formed a bad habit, it’s hard to break.
-
一旦发现问题，请马上告诉我。
If you find any problem, tell me at once.
-
他一旦做了决定，就不会改变。
Once he decides, he doesn’t change his mind.
-
一旦失去信任，就很难再找回来。
Once trust is lost, it’s hard to win back.
-
这种病一旦发现得晚，治疗就很困难。
If this illness is found late, it’s hard to treat.
Words in these examples (34)
| 一旦 | yídàn | in case (sth happens); if; once (sth happens, then...) | HSK 5 |
| 养成 | yǎngchéng | to form (a habit) | HSK 4 |
| 了 | le | (particle marking a completed action or a change) | HSK 1 |
| 坏 | huài | bad; broken | HSK 2 |
| 习惯 | xíguàn | habit; to be used to | HSK 3 |
| 就 | jiù | then; just; right away; only | HSK 2 |
| 很 | hěn | very | HSK 1 |
| 难 | nán | difficult | HSK 3 |
| 改 | gǎi | to change; to correct | HSK 4 |
| 掉 | diào | to fall; to drop | HSK 4 |
| 发现 | fāxiàn | to discover; to find | HSK 3 |
| 问题 | wèntí | question; problem | HSK 1 |
| 请 | qǐng | please; to invite; to treat (pay for) | HSK 1 |
| 马上 | mǎshàng | right away; immediately | HSK 3 |
| 告诉 | gàosu | to tell | HSK 2 |
| 我 | wǒ | I; me | HSK 1 |
| 他 | tā | he; him | HSK 1 |
| 做 | zuò | to do; to make | HSK 1 |
| 决定 | juédìng | to decide; decision | HSK 3 |
| 不 | bù | not; no | HSK 1 |
| 会 | huì | can; to know how to | HSK 1 |
| 改变 | gǎibiàn | to change | HSK 4 |
| 失去 | shīqù | to lose | HSK 4 |
| 信任 | xìnrèn | to trust; to have confidence in | HSK 5 |
| 再 | zài | again | HSK 1 |
| 找 | zhǎo | to look for; to find | HSK 1 |
| 回来 | huílái | to come back | HSK 2 |
| 这 | zhè | this | HSK 1 |
| 种 | zhǒng | kind; type | HSK 3 |
| 病 | bìng | illness; to be ill | HSK 1 |
| 得 | de | (particle after a verb before a description of how it is done, as in 说得很好) | HSK 2 |
| 晚 | wǎn | late; evening | HSK 1 |
| 治疗 | zhìliáo | to treat (an illness); medical treatment; therapy | HSK 5 |
| 困难 | kùnnan | difficult; difficulty | HSK 4 |
Common mistakes
-
✗一旦下雨，才不去。
✓一旦下雨，就不去了。
一旦 pairs with 就.
-
✗我一旦昨天去了。
✓我昨天去了。
一旦 is for conditions, not plain past events.
Check yourself
Choose the word that fills the gap.
1. 开始，就要坚持下去。
2. 一旦发生火灾，大家 要马上离开。
3. 机会一旦错过， 不会再来了。