A tram (U.S. streetcar or trolley) is a vehicle that runs on rails in cities, frequently along streets, where the rails are laid flush with the road surface.
Most trams are powered by electricity from an overhead wire, but they can also be horse-drawn, pulled by underground cable, steam-powered, or powered by electricity from a surface or underground conduit.
Trams have historically been single vehicles, but two or three coupled together have been used in places, and articulated trams are becoming more common.
Many tram systems were closed down in the 1940s to 1960s, but trams have been making a comeback with many new lines opening in recent years. Many tram systems survived in European cities and parts of Asia, but the largest to survive in the English-speaking world is in Melbourne, Australia.