This is the 4th most frequent Polish word.
nie
"Nie" means "no" in English.
The word 'nie' is used as a negation of the verb 'idę' (I am going). It indicates that the action of going is not happening.
Nie idę do sklepu.
I am not going to the store.
In this sentence, 'nie' negates the action 'pada' (rains), meaning that the condition of raining is not occurring.
Nawet jeśli nie pada deszcz, to wezmę parasol.
Even if it is not raining, I will take an umbrella.
Here, 'nie' serves to negate the verb 'jest' (is), suggesting that the subject, 'to' (this), is not what the predicate suggests.