A1
Saying it didn’t happen with 沒
When Chinese uses 沒 rather than 不, why 我不去 and 我沒去 are different sentences, and why 沒 and 了 never appear together.
沒 says something did not happen. Not that you choose not to, not that you never do — that on this occasion, it did not occur.
我沒去。
Wǒ méi qù.
I didn’t go.
他沒來。
Tā méi lái.
He didn’t come.
我還沒吃飯。
Wǒ hái méi chīfàn.
I haven’t eaten yet.
沒有 is the full form and 沒 the short one. Before a verb they are interchangeable and 沒 is more common in speech; before a noun, 沒有 is the verb to not have and cannot be shortened away.
不 and 沒 are not interchangeable
This is the pair that takes longest to feel natural, because English negates everything with one word. The split is not about time exactly — it is about whether you are denying an event or denying a fact.
我不去。
Wǒ bú qù.
I’m not going.
我沒去。
Wǒ méi qù.
I didn’t go.
The first is a decision, and it holds for the future. The second is a report about what did not take place. Both are correct sentences; they simply answer different questions.
我昨天不去。
我昨天沒去。
昨天 puts the sentence in the past, and 不 cannot negate an event that has already failed to happen. The exception is a past habit — 我小時候不吃辣的, I didn’t eat spicy food as a child — which is a standing fact rather than an occasion.
沒 and 了 never appear together
了 marks something as completed. 沒 says it was not. Putting both in one sentence asks it to be two things at once, and the fix is always to drop the 了.
我沒去了。
我沒去。
The completion is already denied by 沒. This mistake is common because English keeps its past marking in the negative — didn’t go still looks past-tense — and Chinese does not.
有 is always negated with 沒
Whatever the time frame. There is no 不有.
我沒有時間。
Wǒ méiyǒu shíjiān.
I don’t have time.
那兒沒有人。
Nàr méiyǒu rén.
There’s nobody there.
Asking about it
The A-not-A form of a 沒 sentence puts 沒有 at the end, which is how you ask whether something has happened yet.
你吃飯了沒有？
Nǐ chīfàn le méiyǒu?
Have you eaten?
Answer it with 吃了 or 還沒.