This is the 1633rd most frequent Polish word.
nieletnich
"Nieletnich" means "minors" in English.
The word 'nieletnich' refers to minors, meaning individuals who are under the legal age of adulthood; in this sentence, it's used to specify the intended users of the playground.
W parku znajduje się plac zabaw dla nieletnich.
In the park, there is a playground for minors.
Here, 'nieletnich' refers to minors, emphasizing the target audience for the internet safety education.
Nieletnich należy edukować o bezpieczeństwie w Internecie.
Minors should be educated about safety on the Internet.
In this sentence, 'nieletnich' (minors) signifies the group of young individuals who are under someone's care.