This is the 2093rd most frequent Polish word.
niedziele
"Niedziele" means "Sundays" in English.
In this sentence, 'niedziele' is used as a plural form of 'niedziela' (Sunday), referring to all Sundays generally.
W niedziele zawsze chodzimy do kościoła.
On Sundays, we always go to church.
Here, 'niedzieli' (a case variation of 'niedziele') is used in a singular context, referring to a specific Sunday in the future.
Nie zapomnij, że mamy czas tylko do przyszłej niedzieli.
Don't forget that we only have time until next Sunday.
In this example, 'niedziele' is employed to refer to Sundays in general as days when the action takes place.