What does the prefix of mean?

The prefix "of" is not a prefix in the traditional sense used in word formation. It's a preposition that indicates possession, origin, or connection.

Here's how it works:

* Possession: "The book of my brother" (the brother owns the book)

* Origin: "The city of Rome" (Rome is the origin of the city)

* Connection: "The sound of music" (the music is connected to the sound)

It doesn't attach to a root word to create a new word. It's a standalone preposition that helps clarify the relationship between words in a sentence.