万一... (wànyī): In Case in Chinese
万一…（就）…
万一 introduces a contingency the speaker considers possible but usually unlikely, unwanted, or worth preparing for. The following clause gives a response or consequence and may use 就, 那, or another result expression. It is stronger than a neutral 如果 because it adds the speaker's concern about what might unexpectedly happen.
Published July 17, 2026
Reviewed July 17, 2026
01 / PATTERN
See the Structure
MODEL
万一 + Condition, Subject + 就 + Response
Read the structure
万一 introduces a contingency the speaker considers possible but usually unlikely, unwanted, or worth preparing for. The following clause gives a response or consequence and may use 就, 那, or another result expression. It is stronger than a neutral 如果 because it adds the speaker's concern about what might unexpectedly happen. Keep the model 万一 + Condition, Subject + 就 + Response visible while you compare each sentence.
万一下雨，我们就改在室内见。
If it happens to rain, we will meet indoors instead.
Choose the right context
To prepare for a possible problem: 万一下雨，我们就改在室内见。 To ask about an unwanted possibility: 万一赶不上最后一班车怎么办？ To give a precautionary reason: 带上充电器，万一手机没电呢？
万一赶不上最后一班车怎么办？
What will we do if we miss the last bus?
Respect the boundary
For a neutral or routinely expected condition; 如果 is usually more suitable. Do not place 万一 after the contingency predicate it is meant to introduce. Do not require 就 in every sentence; questions with 怎么办 and other responses can follow directly.
明天下雨万一，我们就改时间。
(If it happens to rain tomorrow, we will change the time.)
Repair the pattern
万一 is placed after the contingency clause: 万一 introduces the possible event, so it must come before 明天下雨 rather than after the event. 就 is placed before the result-clause subject: In the result clause, put the subject 我们 before the adverb 就: 我们 + 就 + 改.
万一明天下雨，我们就改时间。
Use the repaired structure without changing the intended meaning.
02 / MAP
Read the Sentence
Read from left to right and notice the job performed by each part. The labels describe this example; they are not a rule that every Chinese sentence must copy.
万一下雨，我们就改在室内见。
If it happens to rain, we will meet indoors instead.
万一
万一
This part occupies the 万一 position in the model pattern.
下雨
Condition, Subject
This part occupies the Condition, Subject position in the model pattern.
，
就
This part occupies the 就 position in the model pattern.
我们
Response
This part occupies the Response position in the model pattern.
就
万一
This part occupies the 万一 position in the model pattern.
改
Condition, Subject
This part occupies the Condition, Subject position in the model pattern.
在
就
This part occupies the 就 position in the model pattern.
室内
Response
This part occupies the Response position in the model pattern.
见
万一
This part occupies the 万一 position in the model pattern.
03 / EXAMPLES
Examples You Can Reuse
Keep the structure stable while changing the people, objects, times, or conditions. Pinyin is shown as reading support; use the Chinese sentence and translation to confirm the grammar relationship.
万一下雨，我们就改在室内见。
If it happens to rain, we will meet indoors instead.
万一赶不上最后一班车怎么办？
What will we do if we miss the last bus?
带上充电器，万一手机没电呢？
Bring a charger, in case the phone runs out of power.
04 / LIMITS
When to Use It — and When Not To
Use it when
- To prepare for a possible problem: 万一下雨，我们就改在室内见。
- To ask about an unwanted possibility: 万一赶不上最后一班车怎么办？
- To give a precautionary reason: 带上充电器，万一手机没电呢？
Do not use it when
- For a neutral or routinely expected condition; 如果 is usually more suitable.
- Do not place 万一 after the contingency predicate it is meant to introduce.
- Do not require 就 in every sentence; questions with 怎么办 and other responses can follow directly.
05 / REPAIR
Compare Right and Wrong
Compare the smallest meaningful change. Each explanation identifies a placement, scope, form, or clause relationship instead of treating the whole sentence as one undifferentiated mistake.
明天下雨万一，我们就改时间。
万一明天下雨，我们就改时间。
万一 is placed after the contingency clause
万一 introduces the possible event, so it must come before 明天下雨 rather than after the event.
万一明天下雨，就我们改在室内见。
万一明天下雨，我们就改在室内见。
就 is placed before the result-clause subject
In the result clause, put the subject 我们 before the adverb 就: 我们 + 就 + 改.
明天下雨万一，我们就改时间。
Move 万一 before the contingency: 万一明天下雨。
万一明天下雨，就我们改在室内见。
Put the result-clause subject before 就: 我们就改在室内见。
06 / PRACTICE
Practice the Grammar Point
Complete three short tasks in order: judge the pattern, repair a common error, and build the sentence. Feedback is fixed and reviewed, so these activities do not use a checker allowance.
1. Judge the sentence
2. Choose the correction
3. Build the sentence
Build a complete sentence with 万一…（就）….
07 / APPLY
Apply It in Your Sentence
Write one original sentence with 万一…（就）…. Your draft moves to the checker through this browser session, selects this grammar point as the first review focus, and waits for you to submit.
08 / QUESTIONS
万一... (wànyī): In Case Questions
What is the difference between 万一 and 如果?
如果 presents a condition neutrally. 万一 highlights a possibility that is unexpected, undesirable, or important to prepare for, so it often carries concern.
Does a 万一 sentence need 就?
No. 就 commonly introduces the response, but 万一 can also be followed by 怎么办, 呢, or another result expression when the relationship is clear.
09 / SOURCES
Sources and Review Notes
These references support different parts of the lesson. GF0025-2021 supports level placement only; professional grammar works support the explanation, limits, examples, and cross-checks. Their inclusion does not imply endorsement.
Modern Mandarin Chinese Grammar: A Practical Guide, 3rd ed.
Ross, Ma, Chen, He and Yeh · Routledge · 2024
Locator: Construction index and function chapters relevant to 万一…（就）…
Supports the learner-facing account of where 万一…（就）… appears and what communicative job it performs.
Official sourceChinese: A Comprehensive Grammar, 2nd ed.
Yip and Rimmington · Routledge · 2016
Locator: Relevant sentence and clause chapters for 万一…（就）…
Cross-checks the 万一 + Condition, Subject + 就 + Response pattern, clause relationship, and limits represented by the reviewed examples.
Official sourceChinese Proficiency Grading Standards for International Chinese Language Education (GF0025-2021)
Ministry of Education and State Language Commission · Ministry of Education of the PRC · 2021
Locator: Appendix A, Level 4 grammar inventory
Supports directory placement at HSK 4; it does not independently prove usage rules.
Official source10 / CONTINUE
Continue with a Connected Rule
Compare
一旦…就…一旦...就... (yídàn...jiù)
Distinguish low-probability 万一 from 一旦 presenting a condition as an immediate trigger.
Compare
除非…否则/不然…除非...否则... (chúfēi...fǒuzé)
Compare contingency planning with a necessary-condition frame followed by an otherwise consequence.
Compare
幸亏…要不然…幸亏...要不然...: Luckily
Compare planning for a feared contingency with relief that the feared outcome was avoided.
Continue learning
要是……，就……要是……就…… Everyday Condition
Continue to the everyday 要是就 pattern when the condition is not specially feared.
RECOMMENDED NEXT
Compare
Compare contingency planning with a necessary-condition frame followed by an otherwise consequence.