Elevated railway and Underground railway

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

Underground railway and elevated railway are semantically related in train line topic. In some cases you can use "Underground railway" instead a noun phrase "Elevated railway".

Underground railway noun - Secret aid to escaping slaves that was provided by abolitionists in the years before the American Civil War.

Elevated railway and underground railway are semantically related in train line topic. You can use "Elevated railway" instead a noun phrase "Underground railway".