Terminology

Metro is the most common term for underground rapid transit systems used by non-native English speakers. Rapid transit systems may be named after the medium by which passengers travel in busy central business districts; the use of tunnels inspires names such as subway, underground, Untergrundbahn (U-Bahn) in German, or the Tunnelbana (T-bana) in Swedish; the use of viaducts inspires names such as elevated (L or el), skytrain, overhead, overground or Hochbahn in German. One of these terms may apply to an entire system, even if a large part of the network (for example, in outer suburbs) runs at ground level.

In most of Britain, a subway is a pedestrian underpass; the terms Underground and Tube are used for the London Underground, and the North East England Tyne and Wear Metro, mostly overground, is known as the Metro. In Scotland, however, the Glasgow Subway underground rapid transit system is known as the Subway. In most of North America, underground mass transit systems are primarily known as subways.citation needed The term metro is a shortened reference to a metropolitan area. Chicago's commuter rail system that serves the entire metropolitan area is called Metra, while its rapid transit system that serves the city is called the "L". Rapid transit systems such as the Washington Metro, Los Angeles Metro Rail, the Miami Metrorail, and the Montreal Metro are generally called the Metro. However the Boston subway system is known locally as "The T". In most of Southeast Asia, rapid transit systems are primarily known as MRT (Mass Rapid Transit) or MTR (Mass Transit Railway).