不 vs 不是 (bù vs búshì): negating verbs/adjectives vs nouns
不 negates verbs and adjectives directly (e.g., 不去, 不好). 不是 negates nouns and identity statements (e.g., 不是学生), and also appears before adjectives modified by degree adverbs like 很 or 太 (e.g., 不是很好). The key distinction is predicate type: verb/adjective uses 不; noun or degree-modified adjective uses 不是.
In Chinese, 不 (bù) and 不是 (búshì) both express 'not', but they apply to different predicate types. 不 directly negates verbs and adjectives, attaching immediately before them. 不是 negates nouns or noun phrases (e.g., 'is not a student'), and also negates adjective phrases that include a degree adverb like 很 or 太 (e.g., 'not very good'). Using 不 with nouns or 不是 with a bare adjective (without a degree adverb) is incorrect. Understanding the predicate type and the presence of degree modifiers ensures proper choice.
When to use each
Use 不 to negate verbs (except 有) and adjectives directly. It always appears immediately before the word it negates, e.g., 不去 (bú qù) 'not go', 不好 (bù hǎo) 'not good'. Do not use 不 with nouns or noun predicates – for those, use 不是. Also, 不 cannot be followed by 是 to form a negation; the combination 不是 is a single word with its own usage.
The tone of 不 changes to bú before a fourth-tone syllable (e.g., 不去 bú qù, 不是 búshì), but the written form remains 不.
Use 不是 to negate nouns and noun predicates (identity or classification), e.g., 不是学生 (búshì xuésheng) 'is not a student', 不是书 (búshì shū) 'is not a book'. Also use 不是 before adjectives when they are modified by degree adverbs like 很, 太, 非常, etc., e.g., 不是很好 (búshì hěn hǎo) 'not very good', 不是太贵 (búshì tài guì) 'not too expensive'. In these cases, 不是 negates the entire degree-modified phrase, not the adjective alone.
When 不是 is used with degree-modified adjectives, it often implies a contrast or understatement (e.g., 'not very good' instead of simply 'bad'). It is not used with bare adjectives.
At a glance
| 不 | 不是 | |
|---|---|---|
| Function | Negates verbs and adjectives directly | Negates nouns and identity; also negates degree-modified adjectives |
| Used with nouns? | No (use 不是 instead) | Yes |
| Used with verbs? | Yes (e.g., 不去) | No (except in rhetorical questions like 不是...吗?) |
| Used with bare adjectives? | Yes (e.g., 不好) | No (must have degree adverb) |
| Position | Immediately before verb/adjective | Before the predicate phrase (noun or degree+adjective) |
| Negation of 是 | Not used; 不是 is the negative form of 是 | Is the negative of 是 (to be) |
Examples
- 不是他不是老师。Tā búshì lǎoshī.He is not a teacher.Noun predicate – use 不是.
- 不我不去。Wǒ bú qù.I am not going.Verb – use 不.
- 不这个苹果不好吃。Zhège píngguǒ bù hǎochī.This apple is not tasty.Adjective – use 不 directly.
- 不是她不是很高兴。Tā búshì hěn gāoxìng.She is not very happy.Adjective with degree adverb 很 – use 不是.
- 不是这不是我的书。Zhè búshì wǒ de shū.This is not my book.Noun phrase possession – use 不是.
Common mistakes
- Using 不是 directly before a bare adjective (e.g., ✗ 这不是好) – use 不好 instead.
- Using 不 with nouns (e.g., ✗ 他不学生) – use 不是: 他不是学生.
- Inserting 是 after 不 to negate a verb (e.g., ✗ 不*是*去) – negate verbs directly with 不.
- Avoiding 不是 with degree-modified adjectives (e.g., thinking 不是很好 is wrong) – it is correct and common.
FAQ
- When do I use 不 vs 不是?
- Use 不 to negate verbs and adjectives directly. Use 不是 to negate nouns or noun predicates. Additionally, use 不是 before adjectives that are modified by degree adverbs like 很, 太, or 非常.
- Can 不是 be used with adjectives?
- Yes, but only when the adjective is preceded by a degree adverb such as 很, 太, 非常, etc. For example, 不是很好 'not very good'. Without the adverb, use 不 + adjective (e.g., 不好).
- What is the difference between 他不高兴 and 他不是很高兴?
- 他不高兴 means 'He is not happy' – a direct negation. 他不是很高兴 means 'He is not very happy' – it negates the degree, implying he may be somewhat happy but not very. The nuance is different; 不是 here focuses on the modifier.
- Is 不是 always the negation of 是?
- Yes, 不是 is the negative form of 是 when used with noun predicates. However, it also appears in other structures, such as before degree-modified adjectives, where it serves to negate the entire adjectival phrase.