This is the 3rd most frequent Bulgarian word.
за
The Bulgarian word "за" translates to "for" or "about" in English, depending on context.
Here, 'за' is used to mean 'about', indicating the subject matter of the book.
Четох книга за историята на България.
I read a book about the history of Bulgaria.
Here, 'за' denotes gratitude and the reason or cause behind it.
Благодаря ти за помощта.
Thank you for your help.
In this sentence, 'за' means 'for', showing the intention or responsibility towards nature.