A bicycle, bike, or cycle is a pedal-driven, human-powered vehicle with two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist or a bicyclist.
Bicycles were introduced in the 19th century and now number about one billion worldwide, twice as many as automobiles.They are the principal means of transportation in many regions. They also provide a popular form of recreation, and have been adapted for such uses as children's toys, adult fitness, military and police applications, courier services, and competitive sports.
The basic shape and configuration of a typical bicycle has changed little since the first chain-driven model was developed around 1885.Many details have been improved, especially since the advent of modern materials and computer-aided design. These have allowed for a proliferation of specialized designs for particular types of cycling.
The invention of the bicycle has had an enormous impact on society, both in terms of culture and of advancing modern industrial usage. Several components that eventually played a key role in the development of the automobile were originally invented for the bicycle – e.g., ball bearings, pneumatic tires, chain-driven sprockets, spoke-tensioned wheels, etc.
Uses
Transporting milk churns in Kolkata, India
Bicycles have been and are employed for many uses:
Working bicycle in Amsterdam, Netherlands
Utility: bicycle commuting and utility cycling
Work: mail delivery, paramedics, police, and general delivery.
Recreation: bicycle touring, mountain biking, BMX and physical fitness.
Racing: track racing, criterium, roller racing and time trial to multi-stage events like the Tour of California, Giro d'Italia, the Tour de France, the Vuelta a España, the Volta a Portugal, among others.
Military: scouting, troop movement, supply of provisions, and patrol. See bicycle infantry.
Show: entertainment and performance, e.g. circus clowns. Used as instrument by Frank Zappa.
