This is the 657th most frequent Bulgarian word.
стефан
"Стефан" is a Bulgarian male given name, equivalent to "Stefan" or "Stephen" in English.
The word 'Стефан' in this sentence is a proper noun, serving as the subject of the sentence, referring to a male individual named Stefan.
Стефан е добър приятел.
Stefan is a good friend.
Here, 'Стефан' indicates possession, referring to a book that was owned by the person named Stefan.
Имам книга, която е била на Стефан.
I have a book that belonged to Stefan.
In this sentence, 'Стефан' is again a proper noun, acting as the subject who performs the action of the verb 'visits'.