Expressing "what if" with "wanyi"
Literally meaning "ten thousand [to] one," 万一 (wànyī) is a word you can use to discuss unlikely possibilities in the sense of "what if," or "in case," or "in the unlikely event that." It's most often used to bring up undesirable situations.
万一 is used for a usually undesirable possibility which the speaker considers highly unlikely. It's often a rhetorical question. (In other words, the speaker is saying, "if this happens, you're screwed.")
There are two common ways to use it in a question:
万一 ⋯⋯ 怎么办 ？
万一 ⋯⋯ 呢 ？
Note that 万一 can go before or after the subject of a sentence.
This use of 万一 has the same basic meaning as in a statement, but because it's a question, there's no solution offered.
- 万一 我 父母 不 同意 呢 ？What if my parents disapprove?
- 万一 被 发现 了 怎么办 ？What if we get caught?
- 带 着 伞 吧 ，万一 下雨 呢 ？Take an umbrella. What if it rains?
- 你 先 打 电话 问问 。他 万一 不 在 呢 ？You should call first. What if he's not there?
- 开 慢 点 ！万一 撞到 人 怎么办 ？Drive more slowly! What if you hit someone?
After bringing up the possibility of "disaster," the rest of the sentence normally addresses what "we" should do about it.
万一 ⋯⋯ ，⋯⋯
- 万一 他 不 喜欢，你 可以 来 换 。If he doesn't like it, you can come back and exchange it.
- 我 要 记 下来 ，万一 忘 了，可以 查 。I need to write it down. In case I forget, I can look it up.
- 万一 迷路 了，就 用 地图 导航 。In case you get lost, use the map's GPS navigation.
- 万一 发生 这种 情况 ，马上 报警 。In the unlikely event that this happens, call the police immediately.
以防万一(yǐfángwànyī) as "just in case!"
This usage is notably less common than the other two, but if you're looking to sophisticate your Chinese, this is a good leader phrase to know. (Later on you will learn more about what's going on with this 以.)
- 北京 现在 特别 冷 ，多 带 几 件 衣服 ，以防万一 。It's especially cold now in Beijing. You should bring a few more pieces of clothing, just in case.
- 多 带 点 现金 吧 ，以防万一 。Take some extra cash, just in case.
- 多 买 点 吧 ，以防万一 。We should buy some more, just in case.