This is the 6049th most frequent Polish word.
agnieszkę
The word "agnieszkę" is the accusative form of "Agnieszka," a Polish female given name equivalent to "Agnes" in English.
Direct object form, the name 'Agnieszka' is in accusative case due to the verb action directed at her.
Widzę Agnieszkę w sklepie.
I see Agnieszka in the store.
Instrumental case, used after the preposition 'z' meaning 'with' indicating interaction with Agnieszka.
Rozmawiałem z Agnieszką o książkach.
I talked with Agnieszka about books.
Genitive case, indicating possession where 'Agnieszki' shows that the book belongs to Agnieszka.