Introduction
To say something is not big, not expensive, not difficult, put 不 (bù) straight in front of the adjective. The thing to watch is what happens to 很 (hěn): a positive adjective sentence needs it, and a negative one drops it.
Overview
Structure: Subject + 不 (bù) + Adjective
| Pattern | Example | Translation |
|---|---|---|
| S + 很 + Adj（positive） | 今天很热。(Jīntiān hěn rè.) | It's hot today. |
| S + 不 + Adj | 今天不热。(Jīntiān bú rè.) | It isn't hot today. |
| S + 不太 + Adj | 今天不太热。(Jīntiān bú tài rè.) | It isn't very hot today. |
| S + Adj + 不 + Adj？ | 今天热不热？(Jīntiān rè bu rè?) | Is it hot today? |
| S + 不 + Adj，很 + Adj | 不贵，很便宜。(Bú guì, hěn piányi.) | Not expensive — cheap. |
很 (hěn) disappears in the negative:
- Positive: 这个很贵。(Zhège hěn guì.) — This is expensive. 很 is needed as a filler; without it the sentence sounds like a comparison.
- Negative: 这个不贵。(Zhège bú guì.) ✓ — This isn't expensive.
- ❌ 这个不很贵。(Zhège bù hěn guì.) — grammatical but odd. Say 不太贵 (bú tài guì) for "not very expensive".
- Remember: no 是 (shì) anywhere in these sentences. ❌ 今天是不热。(Jīntiān shì bú rè.)
Examples
今天不冷。
Jīntiān bù lěng.
It isn't cold today.
这个菜不好吃。
Zhège cài bù hǎochī.
This dish isn't tasty.
我的房间不大。
Wǒ de fángjiān bú dà.
My room isn't big.
中文不太难。
Zhōngwén bú tài nán.
Chinese isn't very hard.
他忙不忙？
Tā máng bu máng?
Is he busy?
这件衣服不贵，很便宜。
Zhè jiàn yīfu bú guì, hěn piányi.
These clothes aren't expensive, they're cheap.
Usage Notes
- Tone change: 不 becomes bú before a fourth-tone adjective — 不贵 (bú guì), 不大 (bú dà), 不对 (bú duì). Before other tones it stays bù — 不冷 (bù lěng), 不难 (bù nán).
- In an A-not-A question the second 不 is unstressed and neutral: 大不大 (dà bu dà), 好不好 (hǎo bu hǎo).
- 不太 (bú tài) is the polite way to disagree. 这个菜不好吃 (Zhège cài bù hǎochī) is blunt; 这个菜不太好吃 (Zhège cài bú tài hǎochī) is what people actually say to a host.
- Two-syllable adjectives behave the same: 不高兴 (bù gāoxìng) — not happy, 不舒服 (bù shūfu) — unwell.
- Never use 没 (méi) with an adjective for a present state. 今天没热 (Jīntiān méi rè) is wrong; 没 with adjectives only appears in comparisons, which comes later.