A monorail is a rail-based transportation system based on a single rail, which acts as its sole support and its guideway. The term is also used variously to describe the beam of the system, or the vehicles traveling on such a beam or track. The term originates from joining the words mono (one) and rail, from as early as 1897, possibly from German engineer Eugen Langen

Eugen Langen

Eugen Langen was a German entrepreneur, engineer and inventor, involved in the development of the petrol engine and the Wuppertal monorail. In 1857 he worked in his father's sugar factory, JJ Langen & Söhne, after an extensive technical training at the Polytechnic institute in Karlsruhe.-Otto and...

 who called an elevated railway system with wagons suspended the Eugen Langen One-railed Suspension Tramway (Einschienige Hängebahn System Eugen Langen).