Comparing "bu" and "mei"

Both 不 (bù) and 没 (méi) can be placed in front of a verb or adjective to negate its meaning. However, 不 and 没 are not usually interchangeable, so it's important to learn when you must use 不 as opposed to 没, and vice versa.

不 is for negating in the present and future

不 is generally used to negate an action that you do not want to do or do not intend to do (in the future). So expressing things like "I don't want to go" or "I'm not going" would be uses of 不.

Structure

Subject + 不 + Verb

Examples

Whether it's "don't wanna do it" or "not gonna do it," use 不:

• 我 今天 晚上 不 吃 饭。
• 我 今天 晚上 不 想 吃 饭。
• 他 不 去 公园。
• 他 不 要 去 公园。

不 is used to negate habitual actions

不 can be used to negate habitual actions, to express what you just aren't in the habit of doing, such as eating meat, or watching TV, or drinking alcohol. This is simply done by placing 不 in front of the verb.

• 我 不 吃 肉。
• 我 不 看 电视。
• 我 不 喝 酒。

Please note that, while it is grammatically correct to use 没 in all the sentences above, 没 does not negate any habitual actions. The sentences above, if they contained 没 instead of 不, would express that the speaker didn't do the named activity (at one particular point in the past). So it would not be about habitual actions.

不 is normally used with adjectives

When it comes to a simple negation of an adjective (e.g. "not Adj"), use 不.

Structure

不 + Adj

Examples

• 我 不 高兴。
• 她 不 漂亮。
• 你的 女朋友 不 难看。
• 我们 不 饿。
• 你 不 聪明。

不 is used to ask questions

There a couple ways to use 不 to ask questions. One such way is through affirmative-negative questions. This is done by stating a verb and then immediately repeating that verb in a negative state (with 不):

• 你 是 不 是 我 的 老师。
• 今天 你 来 不 来？
• 你 喜 不 喜欢 吃 中国菜。

不 can also be used to form tag questions. Tag questions use the positive-negative question form, but are placed at the end of the sentence. Tag questions are used to seek approval or acceptance for a statement, very similar to the English "OK?" or "right?" You can't use 没 for this.

• 我们 去 吃饭，好 不 好？
• 你 是 我的 同学，对 不 对？
• 我们 喝 水，好 没 好。
• 你 得 上 课，对 没 对。

没 is used to negate past actions

没 and 没有 can both be used to negate actions that occurred in the past, or to say that something has not happened yet.

• 他 没有 打 电话 给 我。
• 他 没有 上课。
• 我 昨天 没 喝 葡萄酒。
• 我 昨天 不 喝 葡萄酒 。

There are a few things worth noting in these examples. For one, it is still grammatically correct to leave out the 有 in the sentences using 没有. Also, the sentence using 不 would be grammatically correct, if not for the 昨天 ("yesterday") telling us that it is definitely the past we're talking about. That incorrect sentence using 不 would translate into *"I don't drink wine yesterday" as opposed to "I didn't drink wine yesterday."

Only 没 is used to negate 有

没 can be used to negate the verb 有 ("to have") to mean "do not have." You can only use 没 to convey this meaning. It is grammatically incorrect to use 不 to negate 有.

• 我 没有 钱。
• 我 不 有 钱。
• 他 没有 女朋友。
• 他 不 有 女朋友。

There are times when you can leave out 有 entirely while still expressing 没有 (meaning "to not have" or "there is no"). One well-known example of this is 没办法 ("there is no way" [that's gonna happen]). Both 没 and 没有 are correct, however.

• 我 没 办法。
• 我 没有 办法。

(You can also use 没办法 to express other meanings.)

没 is used to make comparisons

没 or 没有 can be used to make simple comparisons meaning "not as... as":

• 我 的 钱 没有 他 的 钱 多。
• 你 的 钱 不 有 他 的 钱 多。
• 你 没有 我 高兴。
• 你 不 有 我 高兴。

You can only use 没 or 没有 for this purpose, and not 不.

不 is used almost exclusively with some verbs

Certain verbs just don't get negated by 没 or 没有 ever. These include the verbs 是 ("to be") and 在 ("to be (in a place)"), as well as some psychological verbs such as 知道 ("to know") and 认识 ("to know (a person)"). For these verbs, it's best to just take them on a case-by-case basis. Being aware of their existence can save you a fair bit of confusion.

• 他 以前 不 是 我的 朋友 。
• 他 以前 没 是 我的 朋友 。
• 昨天 我 不 在 家。
• 昨天 我 没 在 家。
• 昨天 我 不 知道。
• 昨天 我 没 知道。
• 他 以前 不 认识 她 。
• 他 以前 没 认识 她 。

Note that in non-standard Mandarin you might encounter exceptions to this rule. It's still useful to know the rule!