Cycling
Cycling, also, when on a two-wheeled bicycle, called bicycling or biking, is the use of cycles for transport, recreation, exercise or sport. People engaged in cycling are referred to as "cyclists", "bicyclists", or "bikers". Apart from two-wheeled bicycles, "cycling" also includes the riding of unicycles, tricycles, quadricycles, recumbent and similar human-powered vehicles (HPVs).
Bicycles were introduced in the 19th century and now number approximately one billion worldwide. They are the principal means of transportation in many parts of the world, especially in densely populated European cities.
