When do I use 否则 vs 不然?

Use 否则 in formal or written contexts (e.g., rules, official instructions, academic writing) to mean 'otherwise'. Use 不然 in everyday speech for 'otherwise' or to make a suggestion (e.g., '不然我们试试？' – 'How about we try?').

Can 不然 be used in formal writing?

It is not recommended. 不然 is colloquial; in formal texts like contracts, manuals, or academic papers, use 否则 or other formal conjunctions.

Does 不然 always mean 'otherwise'?

Not always. In the suggestion usage, 不然 introduces an alternative (like 'how about'). It also literally means 'not so' in some contexts (e.g., '不然吧' – 'Not really'). But the most common meanings are 'otherwise' and as a suggestion marker.

What is a good example of the suggestion function of 不然?

Example: '我们不想吃饭，不然去喝咖啡？' (We don't want to eat; how about going for coffee?). Here 不然 cannot be replaced by 否则.

Easily confusedHSK 5

否则 vs 不然 (fǒuzé vs bùrán): formal vs colloquial 'otherwise'

Both 否则 (fǒuzé) and 不然 (bùrán) mean 'otherwise' or 'or else', but they differ in register and function. 否则 is formal, used in writing and serious speech, while 不然 is colloquial and can also introduce a friendly suggestion ('how about'). Use 否则 for conditional warnings and 不然 for everyday alternatives or suggestions.

The core difference is register: 否则 is formal and reserved for written language, official warnings, or serious consequences; 不然 is the informal equivalent used in daily conversation. Additionally, 不然 has a unique function as a suggestion marker, equivalent to 'how about' or 'why don't we', which 否则 never fills. In the 'otherwise' sense, they are interchangeable but rarely in the same context due to formality.

When to use each

否则fǒuzé

otherwise; or else (formal)

Use 否则 in formal or serious contexts such as academic writing, legal documents, public announcements, or strong warnings. It always introduces the consequence if a condition is not met, and it cannot be used to make suggestions.

不然bùrán

otherwise; or else; or how about (colloquial)

Use 不然 in everyday speech, informal writing, or casual conversation. It can mean 'otherwise' more flexibly, and it also serves as a suggestion opener: '不然……?' (how about...?). In the 'otherwise' sense it is less formal than 否则.

When used for suggestions, 不然 often begins the suggestion clause and implies an alternative course of action, e.g., 不然我们走吧 ('How about we leave?'). This is a common colloquial usage that does not exist with 否则.

At a glance

	否则	不然
Register	Formal; written, official, or serious speech	Informal; everyday conversation and casual writing
Suggestion marker	Not used for suggestions	Can introduce a suggestion: '如何？/要不要？'
Typical context	Conditional warnings, contracts, academic reasoning	Alternatives in daily life, recommendations, light warnings
Negation particle	否 (fǒu) is a formal negation	不 (bù) is standard colloquial negation

Examples

否则
请按时完成作业，否则会影响你的成绩。
Qǐng ànshí wánchéng zuòyè, fǒuzé huì yǐngxiǎng nǐ de chéngjì.
Please finish the homework on time, otherwise it will affect your grades.
Formal instruction; 否则 is appropriate in a school notice or formal reminder.
不然
你快点准备，不然来不及了。
Nǐ kuài diǎn zhǔnbèi, bùrán láibují le.
Hurry up and get ready, otherwise we'll be late.
Informal warning between friends; 不然 fits naturally.
不然
不然我们周末去爬山吧？
Bùrán wǒmen zhōumò qù páshān ba?
How about we go hiking this weekend?
Suggestion usage: 不然 introduces an alternative idea. 否则 cannot be used here.
否则
根据规定，必须携带身份证，否则不得入场。
Gēnjù guīdìng, bìxū xiédài shēnfènzhèng, fǒuzé bùdé rùchǎng.
According to regulations, you must bring your ID card, otherwise entry is not allowed.
Formal rule; 否则 is correct. Using 不然 here would sound too casual.
不然
你穿上外套吧，不然会冷。
Nǐ chuān shàng wàitào ba, bùrán huì lěng.
Put on a coat, or you'll get cold.
Casual advice between friends; 否则 would be overly formal.

Common mistakes

Using 否则 in casual conversation: '否则我们走吧' sounds stiff — use 不然.
Using 不然 in formal writing: e.g., a legal document saying '不然将罚款' is too informal — use 否则.
Using 否则 to make a suggestion: '否则我们看电影？' is wrong — 否则 cannot start a suggestion; use 不然.
Confusing the negation: 否则 contains 否 (formal 'not'), while 不然 contains 不 (colloquial 'not'). Matching register helps choose the right term.

FAQ

When do I use 否则 vs 不然?: Use 否则 in formal or written contexts (e.g., rules, official instructions, academic writing) to mean 'otherwise'. Use 不然 in everyday speech for 'otherwise' or to make a suggestion (e.g., '不然我们试试？' – 'How about we try?').
Can 不然 be used in formal writing?: It is not recommended. 不然 is colloquial; in formal texts like contracts, manuals, or academic papers, use 否则 or other formal conjunctions.
Does 不然 always mean 'otherwise'?: Not always. In the suggestion usage, 不然 introduces an alternative (like 'how about'). It also literally means 'not so' in some contexts (e.g., '不然吧' – 'Not really'). But the most common meanings are 'otherwise' and as a suggestion marker.
What is a good example of the suggestion function of 不然?: Example: '我们不想吃饭，不然去喝咖啡？' (We don't want to eat; how about going for coffee?). Here 不然 cannot be replaced by 否则.