This is the 836th most frequent Russian word.
серии
The Russian word "серии" translates to "series" in English, referring to a set or sequence of related things.
Here, 'серии' is used to denote the serialization of a book.
Эту книгу я читал только в одной серии.
I read this book only in one series.
In this context, 'серия' refers to an individual episode in a series.
На канале начинается новая серия фильма.
A new episode of the movie series is starting on the channel.
Here, 'серий' (genitive plural form of 'серия') means collections or sets of lectures.