object of the preposition

Every preposition must have an object. Together, they make up a prepositional phrase. You can find the object of a preposition by asking “what?”.

I slept under the bridge that night.

Under what? Under the bridge.
In English, an OP is always objective case.
 

Greek:

In Greek, the meaning of the preposition changes based on the case of the OP (BBG 8.3).
 

Hebrew:

See more on this page or this video.