Overhead railway and Railway system

Overhead railway noun - A railway that is powered by electricity and that runs on a track that is raised above the street level.

Railway system and overhead railway are semantically related. In some cases you can use "Railway system" instead a noun phrase "Overhead railway".

Railway system noun - Line that is the commercial organization responsible for operating a system of transportation for trains that pull passengers or freight.

Overhead railway and railway system are semantically related. Sometimes you can replace phrase "Overhead railway" with "Railway system", this phrases are similar.