不 vs 没: "I Don't Eat" or "I Haven't Eaten"?
Compare preferences, actions that have not happened, and "not having" with simple examples.
Two negatives, different jobs
不 and 没 can both correspond to English "not," but they are not interchangeable. Start with these common patterns rather than trying to reduce everything to one tense rule.
不: habits, preferences, intentions, and descriptions
Example
我不吃牛肉。
I do not eat beef.
This can describe a preference or dietary restriction.
Example
我明天不去。
I am not going tomorrow.
Example
我不忙。
I am not busy.
没: an action has not happened
Example
我没吃早饭。
I have not eaten breakfast / I did not eat breakfast.
The surrounding situation determines which English translation fits.
Example
我昨天没去。
I did not go yesterday.
For completed-action negation, beginners can normally use 没＋verb without completed-action 了. Do not mechanically combine them as 没吃了.
没有: not having
Example
我没有时间。
I do not have time.
In ordinary beginner Mandarin, negate 有 with 没有, not 不有.
Compare the meaning
Example
我不喝咖啡。
I do not drink coffee.
Example
我没喝咖啡。
I have not drunk coffee / I did not drink coffee.
The first often describes a habit or choice. The second says the action has not happened in the relevant situation.
Quick practice
Example
我不吃牛肉。
You avoid beef.
Example
我没吃早饭。
You have not eaten breakfast.
Example
我没有时间。
You have no time.
These are useful starting patterns. 不 is not simply "present" and 没 is not simply "past"; the meaning of the sentence matters.