In case / what if with 万一

Structure 万一 + (unlikely case)，…

万一 (wànyī) raises an UNLIKELY but possible case, with a hint of worry: "in case, what if…". 带上伞，万一下雨呢 = "take an umbrella, in case it rains". It opens the condition. It’s like 如果, but only for the improbable that’s worth preparing for.

Examples

万wàn一yī下xià雨yǔ怎zěn么me办bàn？
What if it rains?
带dài上shàng伞sǎn，万wàn一yī下xià雨yǔ呢ne。
Take an umbrella, in case it rains.
万wàn一yī他tā不bù来lái，我wǒ们men就jiù自zì己jǐ去qù。
In case he doesn’t come, we’ll go by ourselves.

Levels are indicative: they follow the standard Chinese Grammar Wiki (AllSet Learning) progression, not an official HSK 3.0 mapping. We never assign levels by eye.

This point and the other 370, with audio on every example, inside Wanyu.