This is the 424th most frequent Croatian word.
završio
"Finished" or "completed."
The word 'završio' is used to indicate the completion of an activity, in this case, finishing reading a book.
Završio sam knjigu koju sam čitao tjednima.
I finished the book I was reading for weeks.
In this sentence, 'završio' describes the act of graduating from university, marking the conclusion of the studies.
Prošle godine završio je fakultet i počeo raditi.
Last year, he completed university and started working.
Here, 'završio' is used to signify the end of an event, specifically a meeting.