不 bù
不 goes right before the word it’s negating — an adjective, a verb, or one of two special verbs that always need it. On top of that, 不 itself sometimes changes tone, which this page covers at the end.
一 不 + Adjective
Put 不 right before an adjective to say something is NOT that way.
二 不 + Verb
不 is also used before a verb, but here it’s about a choice — something you decide not to do, not just a fact about the world.
不 is only for decisions and intentions — if you’re negating a fact (something that did or didn’t happen), you need 没 méi instead. See 不 bù and 没 méi for the full comparison. 別 bié is a third option, used to tell someone not to do something. See the related posts at the bottom of the page.
三 不 + 是 shì or 姓 xìng
These two verbs always use 不 to say “not” — never any other negation word. 姓 xìng (“to have the last name…”) counts as a verb in Chinese, even though it doesn’t feel like one in English.
四 Tone Changes
不 is normally 4th tone (bù), but it changes depending on the tone of the word right after it.
1. Stays bù (4th tone)
When the next word is 1st, 2nd, or 3rd tone, 不 keeps its normal 4th tone.
2. Changes to bú (2nd tone)
When the next word is 4th tone (or a neutral tone that came from a 4th tone), 不 switches to 2nd tone instead.
五 Common Mistakes
❌ 不要
✅ 不要
要 is 4th tone, so 不 has to switch to bú. Keeping 不 at bù here is the single most common tone mistake with this word.
❌ 我不看電影我不看电影
✅ 我沒看電影我没看电影
To say you didn’t do something that already happened (or didn’t happen), use 没, not 不. 不 is for decisions, not for reporting what did or didn’t happen.
❌ 他沒姓李他没姓李
✅ 他不姓李
姓 always pairs with 不, never 没 — no exceptions, even though it’s about a fact rather than a choice.
六 Practice
Pick the correct tone for 不 in each word.
不要 (want)
不想 (want to)
不可以 (may)
不知道 (know)
不懂 (understand)
不去 (go)
不來来 (come)
不睡覺睡觉 (sleep)
不喜歡喜欢 (like)
不方便 (convenient)
不大 (big)
不小 (small)
不長长 (long)
不短 (short)
不胖 (fat)
不瘦 (thin)
不能 (able to)
不會会 (can/will)
