「否则/不然/要不然」fǒuzé / bùrán / yàobùrán

Otherwise / Or Else: 否则 / 不然 / 要不然

Meaning: Otherwise / Or else (否则 formal; 不然 neutral; 要不然 colloquial/suggestive)

Pattern

Although "否则", "不然", and "要不然" all mean "otherwise / or else", HSK 7-9 tests their stylistic and functional differences:
(1) "否则" (fǒuzé — otherwise / failing which): the most formal and written of the three, heavily used in laws, contracts, reports, and speeches (e.g., 企业必须创新，否则将被市场淘汰).
It ONLY expresses negative consequences and can NEVER introduce a casual suggestion.
(2) "不然" (bùrán — otherwise): neutral and versatile in both speech and writing.
(3)

1
快走吧,否则就赶不上车了。
Kuài zǒu ba, fǒuzé jiù gǎn bù shàng chē le.
Hurry up and go, otherwise you won't catch the bus.
2
我们必须立即行动,不然后果不堪设想。
Wǒmen bìxū lìjí xíngdòng, bùrán hòuguǒ bùkān shèxiǎng.
We must take immediate action, otherwise the consequences will be unimaginable.
3
你最好提前准备,要不然临时来不及。
Nǐ zuìhǎo tíqián zhǔnbèi, yàobùrán línshí láibují.
You'd better prepare in advance, or else you won't make it in time at the last minute.
4

•否则 is the most formal (legal/reports); 要不然 / 要不 is the most colloquial and can also propose an alternative ("How about instead...").

⚠️ Common Mistakes:

•Using colloquial 要不然 in solemn legal statutes or formal contracts: use 否则 instead.

•Overusing stiff 否则 in warm, casual everyday chat where 要不然 or 不然 is more natural.

•Omitting the comma or pause before 否则 at the boundary between the two clauses.

•Using 否则 to make an alternative suggestion (*否则我们去吃饭吧 -> 要不/要不然我们去吃饭吧).

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