不是 vs 非 (búshì vs fēi): spoken vs formal negation
The most important distinction is that 不是 is the standard spoken negation for the copula 是, meaning 'is/am/are not', while 非 is a literary and formal word meaning 'is not' or 'non-', primarily used in fixed expressions, formal writing, and as a prefix (e.g., 非会员). In everyday speech, 非 is rarely used alone as a copula negation.
Both 不是 and 非 express negation, but they operate at different stylistic levels. 不是 is the everyday negated form of 是, used in all registers of spoken and written Chinese to mean 'is not'. 非 is a classical Chinese word that appears in formal writing, set phrases, and as a prefix meaning 'non-'; it cannot freely replace 不是 in modern speech without sounding archaic.
When to use each
Use 不是 to negate the copula 是 in modern Mandarin for all persons and numbers. It is the standard way to say 'is not', 'am not', or 'are not' in both spoken and written contexts. It also appears in question tags like 是不是? to confirm something.
Use 非 in formal or literary contexts where 'is not' or 'non-' is needed. Common in fixed expressions like 非也 'that is wrong' (formal), as a prefix meaning 'non-' (e.g., 非官方 'unofficial', 非营利 'non-profit'), and in the construction 非...不可 to express necessity ('have to'). It is not used in ordinary speech as a simple copula negation.
When 非 appears alone as a copula negation (e.g., in classical quotes or very formal writing), it is highly literary and should be avoided in everyday conversation.
At a glance
| 不是 | 非 | |
|---|---|---|
| Register | Everyday spoken and written | Formal, literary, or technical |
| Copula negation of 是 | Standard; e.g., 他不是医生 | Archaic/exceptional; only in classical phrases or very formal prose |
| Use as prefix (non-) | No; 不是 cannot be used as a prefix | Yes; e.g., 非会员 'non-member', 非金属 'non-metal' |
| Position in sentence | Directly before the noun/adjective/verb it negates (as part of copula) | Often attached as a bound morpheme; or before the entire verb phrase in constructions like 非...不可 |
| Typical constructions | 不是X (来否定X) | 非X(不可), 非也, 非但 |
Examples
- 不是他不是老师。Tā búshì lǎoshī.He is not a teacher.Standard everyday negation of copula.
- 不是这手机不是我的。Zhè shǒujī búshì wǒ de.This phone is not mine.Negation of possessive 是.
- 非非会员不得入内。Fēi huìyuán bùdé rùnèi.Non-members may not enter.非 used as prefix meaning 'non-'.
- 非非也，此乃误会。Fēiyě, cǐ nǎi wùhuì.No, this is a misunderstanding.Classical set phrase 非也; highly formal.
- 非我非去不可。Wǒ fēi qù bùkě.I must go (lit. 'cannot but go').非...不可 construction expressing necessity.
Common mistakes
- Using 非 to negate a copula in casual speech, e.g., 他非医生 instead of 他不是医生 — use 不是.
- Using 不是 as a prefix for 'non-', e.g., 不是会员 instead of 非会员 — use 非.
- Assuming 非 can replace 不是 in all contexts, e.g., in 不是……而是…… structures — this is incorrect.
- Overusing 非 in everyday conversation, which sounds overly literary or pretentious.
FAQ
- When do I use 不是 vs 非?
- Use 不是 for ordinary negation of the copula 'to be' in modern speech and writing. Use 非 in formal writing, fixed expressions (e.g., 非也), as a prefix mean 'non-' (e.g., 非官方), and in the construction 非...不可 expressing necessity. In daily conversation, stick to 不是.
- Can 非 be used as a simple copula negation like 不是?
- In modern Mandarin, it is extremely rare and only appears in highly literary or classical contexts (e.g., classical idioms or formal legal text). For everyday negation, always use 不是.
- Is 非 only used in ancient Chinese?
- No, 非 is still productive in modern formal and technical vocabulary (e.g., 非金属 'non-metal', 非暴力 'nonviolence') and in set phrases like 非但 'not only'. However, as a verb meaning 'is not', it is limited to very formal writing.