Cycling, also known as bicycling or biking, is the use of bicycles for transport, recreation, exercise or sport. People engaged in cycling are referred to as “cyclists”, “bikers”, or less commonly, as “bicyclists”. Apart from two-wheeled bicycles, “cycling” also includes the riding of unicycles, tricycles, quadracycles and similar human-powered vehicles (HPVs). Bicycles were introduced in the late 19th century and now number approximately one billion worldwide. They are the principal means of transportation in many parts of the world.
The basic shape and configuration of a typical upright or “safety bicycle”, has changed little since the first chain-driven model was developed around 1885. However, many details have been improved since then. Especially since the advent of modern materials and computer-aided design, there have been significant changes in the detail components of bicycles. In addition to occasional refinements such as lighter weight frames and wheels there have been technological advances such as gears, brakes and transmission that have greatly improved performance and convenience.