---
title: "一旦 (yídàn) in Chinese Grammar: Once (if ever), With Examples"
description: "一旦 (yídàn): once (if ever); as soon as. 一旦 A 就 B: once A happens, B follows. 2 real lines from stories, each word explained."
canonical: "https://mandarinthewild.com/chinese-grammar/yidan"
author: "Mandarin The Wild"
---

[Chinese grammar](https://mandarinthewild.com/chinese-grammar)

# 一旦 yídàn

Once (if ever); as soon as

一旦 A 就 B: once A happens, B follows.

## In stories

**一旦**发现电池冒烟、鼓包或者发出异响，应立即远离，并拨打火警电话119。

[电动车为什么不能进电梯？ · Why are e-bikes banned from lifts in China?](https://mandarinthewild.com/library/read/why-are-e-bikes-banned-from-lifts-in-china#library-word-912-914) HSK 6

原来他忽然想到：今日虽然逍遥，将来年老体衰，暗中自有阎王管着，**一旦**身亡，岂不白活一世？

[拜师学艺 · A Teacher Across the Sea](https://mandarinthewild.com/library/read/a-teacher-across-the-sea-journey-to-the-west-advanced-chinese-2#library-word-39-41)

[Read 电动车为什么不能进电梯？](https://mandarinthewild.com/library/read/why-are-e-bikes-banned-from-lifts-in-china#library-word-912-914)

## More patterns

- [一…就… as soon as …, …](https://mandarinthewild.com/chinese-grammar/yi-jiu)
- [verb + 一 + verb … a little; give it a try](https://mandarinthewild.com/chinese-grammar/v-yi-v)
- [一…，…就… as soon as …, …](https://mandarinthewild.com/chinese-grammar/yi-comma-jiu)
- [一 + measure word (+ noun) + 也/都 + 不/没 not a single …](https://mandarinthewild.com/chinese-grammar/yi-cl-ye-bu)
- [跟/和…一样 the same as …](https://mandarinthewild.com/chinese-grammar/gen-yiyang)
- [像…一样/似的 like …; as … as …](https://mandarinthewild.com/chinese-grammar/xiang-yiyang)

## What does 一旦 (yídàn) mean in Chinese?

Once (if ever); as soon as. 一旦 A 就 B: once A happens, B follows.

## How common is 一旦?

It comes up in 2 readings of the 392 stories and articles in our free Library.

## Does it correct my mistakes?

No. It shows which patterns a text uses and what each one does; it doesn’t mark errors. Paste a sentence you wrote to see whether it uses the pattern you meant.

## More free tools

- [Chinese dictionary](https://mandarinthewild.com/chinese-dictionary)
- [Measure words](https://mandarinthewild.com/measure-words)
- [How hard is this text?](https://mandarinthewild.com/text-level)
- [Free Chinese stories](https://mandarinthewild.com/library)

Patterns found by our own parser; lines from our free Library.