要不 / 要不然【yàobù / yàobùrán】

要不 has two jobs in speech. The more common one puts forward a suggestion: "how about", "why don't we". It comes at the start of the clause, and the sentence usually ends in 吧.

What comes before it is often the reason. 要不 can also open a turn on its own, when the reason is plain from the situation.

Otherwise

Between two clauses, 要不 and 要不然 mean "otherwise", "or else": the first clause says what to do, the second says what happens if you don't. 要不然 is the slightly fuller form; the meaning is the same.

不然 means the same "otherwise" and is the plainer word.

要不 or 要不是

要不是 looks close but means "if it weren't for", and looks back at something that did happen.

• × 要不是我们去吃饭吧 → 要不我们去吃饭吧