This is the 8016th most frequent Polish word.
nastolatka
Teenage girl.
Here, 'nastolatka' is used as the subject of the sentence, referring to a teenage girl in the nominative case.
Nastolatka czyta książkę w parku.
The teenage girl is reading a book in the park.
In this sentence, 'nastolatkę' is in the accusative case, as it is the direct object of the verb 'saw'.
Widziałem tę nastolatkę na koncercie.
I saw that teenage girl at the concert.
Here, 'nastolatki' is in the dative case, used after the preposition 'dla' (for), indicating the recipient of the gift.