This is the 2937th most frequent Polish word.
nastolatków
"Teenagers" or "adolescents."
The word "nastolatków" is the genitive plural case of "nastolatek", used here to denote a group possessing or involved in an activity on the field.
Grupa nastolatków grała w piłkę na boisku.
A group of teenagers was playing football on the field.
In this sentence, "nastolatków" is used in the genitive plural case, indicating individuals belonging to a larger set.
Nie znam wszystkich nastolatków mieszkających w moim bloku.
I don't know all the teenagers living in my apartment building.
Here, "nastolatków" is in the genitive plural, integrated within the context of understanding concerns.