This is the 1791st most frequent Polish word.
zachodniej
The Polish word "zachodniej" means "western" (feminine singular or genitive/dative/lokative form).
The word "zachodniej" is used as an adjective in the genitive case, modifying "części" to denote its location in the west.
Jestem z zachodniej części Polski.
I am from the western part of Poland.
Here, "zachodniej" describes "Europy" and reflects the regional characteristic (western Europe) in the genitive case.
Kultura zachodniej Europy jest dla mnie fascynująca.
The culture of Western Europe is fascinating to me.
"Zachodniej" serves as an adjective in the genitive case, qualifying "szkoły" to indicate it belongs to the western design school.