Bicycle

A bicycle, or bike, can be defined generally as a pedal-driven human-powered vehicle with two wheels attached to a frame, one behind the other. The International Union of Cycling adds the provision that the seat be more or less above the pedals, thus excluding recumbent bicycles.
First introduced in 19th-century Europe, bicycles evolved quickly into the design pictured. Numbering over a billion worldwide, bicycles provide the principal means of transportation in many regions, are a popular form of recreation, and have been adapted for use in many other fields of human activity, including children's toys, adult fitness, military and local police applications, courier services, and cycle sports.
The basic shape and configuration of the bicycle's frame, wheels, pedals, saddle, and handlebars have hardly changed since the first chain-driven model was developed around 1885 , although many important details have since been improved, especially since the advent of modern materials and computer-aided design. These have allowed for a proliferation of specialized designs for individuals who pursue a particular type of cycling.
The bicycle has affected history considerably, in both the cultural and industrial realms. In its early years, bicycle construction drew on pre-existing technologies; more recently, bicycle technology has, in turn, contributed ideas in both old and newer areas.