要不（然）
otherwise, or else; (in suggestions) how about …
Structure
应该做的事 ， 要不（然） 不好的结果 ／ 要不 建议
What it means
“Otherwise, or else”: the first clause says what should happen, the second the bad result if it doesn’t. In speech 要不 also makes a suggestion: “how about …”.
How it is built
What should happen，要不（然）+ bad result, usually with 就 or 会: 快点儿起床，要不就赶不上早读了 (get up, or you’ll miss morning reading). Suggestion: 要不我们去问问老师？
When to use it
Everyday; 否则 says the same as 要不然 in writing. As a suggestion, 要不 opens the clause and it ends in 吧 or a question: 要不…吧／…？
Watch out
Don’t confuse it with 要不是, “if it were not for”: 要不是你提醒我，我就忘了 (if you hadn’t reminded me, I’d have forgotten).
Examples
快点儿起床，要不就赶不上早读了。
Get up quickly, or you’ll miss morning reading.
出门多穿点儿，要不然会感冒的。
Wrap up warmly when you go out, otherwise you’ll catch a cold.
这道题太难了，要不我们去问问老师？
This question is too hard; how about we go and ask the teacher?
Learn this in Lesson 17 · HSK 5: 中学生的一天 (A school day in China)
A dialogue, a reading, word cards with audio and a drill that uses it, in Learn Chinese with Bao. The first lessons of every level are free.
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