Prepositions of Agents or Things:

Prepositions of agents or things indicate a casual relationship between nouns and other parts of the sentence.

Of, for, by, with, about, etc. are the most used and common prepositions of agents or things.

Example:

. This article is about smartphones.

. Most of the guests have already left.

. I will always be here for you.

. He is playing with his brothers.