This is the 3035th most frequent German word.
bekannter
"Bekannter" means "acquaintance" in English.
In this sentence, 'Bekannter' is used as a noun meaning 'acquaintance', referring to a person the speaker knows casually.
Ein Bekannter hat mir das Buch empfohlen.
An acquaintance recommended the book to me.
In this sentence, 'bekannt' as an adjective is used to mean 'well-known'. It describes the restaurant's popularity or recognition in the area.
Dieses Restaurant ist hier sehr bekannt.
This restaurant is very well-known here.
Here 'bekannten' functions as an adjective describing the noun 'author', specifying the author's status as being famous or renowned.