This is the 14978th most frequent Polish word.
rozdziałów
"Chapters" (genitive plural form).
Here, 'rozdziałów' is used as the plural form in the genitive case to describe divisions or sections of a book.
Autor książki podzielił ją na kilka rozdziałów.
The author of the book divided it into several chapters.
In this sentence, 'rozdziałów' is in the genitive case referring to the chapters read, indicating quantity.
Czytałem wiele rozdziałów, ale jeszcze nie ukończyłem książki.
I read many chapters, but I have not finished the book yet.
The word 'rozdziałów' again appears in the genitive case, used to complement the noun 'liczbę', referring to the object of counting.