A train is a form of transport consisting of a series of connected vehicles that generally runs along a rail track to transport cargo or passengers. The word train comes from the Old French trahiner, derived from the Latin trahere meaning to pull or to draw.[1]

Motive power for a train is provided by a separate locomotive or individual motors in a self-propelled multiple unit. Although historically steam propulsion dominated, the most common types of locomotive are diesel and electric, the latter supplied by overhead wires or additional rails. Trains can also be hauled by horses, pulled by engine or water-driven cable or wire winch, run downhill using gravity, or powered by pneumatics, gas turbines or batteries.

Train tracks usually consist of two running rails, sometimes supplemented by additional rails such as electric conducting rails and rack rails. Monorails and maglev guideways are also used occasionally.[2]

A passenger train includes passenger-carrying vehicles and can often be very long and fast. One notable and growing long-distance train category is high-speed rail. In order to achieve much faster operation at speeds of over 500 km/h (310 mph), innovative maglev technology has been the subject of research for many years. The term light rail is sometimes used to refer to a modern tram system, but it may also mean an intermediate form between a tram and a train, similar to a heavy rail rapid transit system. In most countries, the distinction between a tramway and a railway is precise and defined in law.