This is the 117th most frequent Czech word.
ne
"Ne" means "no."
In this sentence, 'ne' serves as part of the verb negation 'nejsi' (you are not).
Nejsi student této školy, že?
You are not a student of this school, are you?
The word 'ne' is used here to explicitly express disagreement or a negative response.
Ne, dnes nemám čas.
No, I don't have time today.
The word 'ne' here functions as a negation prefix for the verb, altering its meaning to express the negative.