不 没
Pattern
不 + verb/adjective / 没(有) + verb
Key words
Core idea
不 and 没 both negate, but they answer different questions. 不 often rejects a quality, habit, choice, willingness, or future intention. 没 says something did not exist or did not happen.
For beginner action sentences about a missed event, 没 is often the more natural option.
Mini decision rule
Ask whether you are negating a general state or the occurrence of an event. That single question solves many early 不 and 没 mistakes.
Completed-action 了 does not stay in ordinary negative completed-event sentences. If the action did not happen, use 没 before the verb and leave out verbal 了.
Use 不 naturally with adjective predicates and stable preferences. Use 没 naturally with possession, existence, and past non-occurrence.
Compare with completed action
The connection with 了 is practical: completed-action marking says an event is done, while 没 says the event did not happen. Those meanings normally do not sit on the same verb in beginner sentences.
Examples
我不喝咖啡。
Wǒ bù hē kāfēi.
I do not drink coffee.
不 can negate a general habit or preference.
我今天没喝咖啡。
Wǒ jīntiān méi hē kāfēi.
I did not drink coffee today.
没 negates an action that did not occur.
他不忙。
Tā bù máng.
He is not busy.
Common mistakes
Avoid
我昨天不去学校。
Use
我昨天没去学校。
For a past event that did not happen, 没 is usually the natural choice.
Avoid
他没忙。
Use
他不忙。
Use 不 to negate ordinary adjective predicates.