Something that was really confusing for me when I first started learning Chinese was when to use 不 and to use 沒. So here’s a handy guide for anyone else who might be facing the same struggle!
speaking in the present or future tense
speaking about someone’s personal decision or willingness
我不去。 (means ‘I didn’t go’ but subtly implies ‘I don’t want to go and therefore have made the decision not to’)
talking about habitual actions
(沒 isn’t ungrammatical in the above cases, it just doesn’t mean the same thing!)
to ask questions!（referred to as ‘verb not verb’ structure)
（沒 is ungrammatical in the above cases）
used exclusively with the verbs 是, 在, and some psychological verbs like 知道 and 認識 (you’ll have to memorize these on a case to case basis)
to speak about the past or perfect tense, also to describe something that hasn’t taken place
so if you see 了 with the verb you’re negating, use 沒
good to note that if a sentence says ‘昨天,’ then you should stay away from using 不!
don’t forget that 沒 is just the shortened form of 沒有, and the two can usually be used interchangeably
and it can be used to express that ‘there isn’t/aren’t’ or that you ‘don’t have’ something
is the only grammatical negation for 有!
can be used for comparison
And one last important thing to note is that using one over the other results in a very different meaning. For example:
我不吃晚飯。 I don’t eat dinner.
我沒吃晚飯。 I haven’t yet eaten dinner.
