Level 4 · Upper Intermediate
What if: 万一
万一 + Bad possibility（，怎么办 / 呢） · Traditional: 萬一 + Bad possibility（，怎麼辦 / 呢）
万一 (wànyī, literally "one in ten thousand") raises an unlikely BAD possibility so you can plan for it: 万一下雨怎么办？"what if it rains?" 带着伞吧，万一下雨呢 "take an umbrella — just in case it rains".
如果 is the neutral "if" for any condition; 万一 adds worry — you hope it won't happen, but you're preparing anyway. (The one playful exception: a hoped-for long shot with 呢 — 买张彩票，万一中了呢 "buy a ticket — what if you win!") Ordinary good or neutral conditions still take 如果 or 要是.
Examples
万一下雨怎么办？
萬一下雨怎麼辦？
wàn yī xià yǔ zěn me bàn
What if it rains?
带着伞吧，万一下雨呢。
帶著傘吧，萬一下雨呢。
dài zhe sǎn ba wàn yī xià yǔ ne
Take an umbrella — just in case it rains.
多带点钱，万一不够呢。
多帶點錢，萬一不夠呢。
duō dài diǎn qián wàn yī bù gòu ne
Bring some extra money, in case it's not enough.
早点出门吧，万一路上人多呢。
早點出門吧，萬一路上人多呢。
zǎo diǎn chū mén ba wàn yī lù shang rén duō ne
Leave a bit early — what if the roads are crowded?
Common mistakes
✗ 万一明天天气好，我们就去公园吧。
✓ 如果明天天气好，我们就去公园吧。
万一 is reserved for unwanted possibilities — neutral or good conditions take 如果.
Related grammar points
Practice this pattern in graded stories like The Heavy Backpack (Part 1) inside the Literate Chinese app.
