Definition: Bicycle(noun) - two-wheeled vehicle operated by pedals
..A bicycle is a pedal-driven, human-powered vehicle with two wheels attached to a frame, one behind the other.
The basic shape and configuration of a typical bicycle has hardly changed since the first chain-driven model was developed around 1885. First introduced in 19th-century Europe, bicycles now number over one billion worldwide providing the principal means of transportation in many regions like China and the Netherlands. Bikes are also a popular form of recreation. Bicycles have been adapted for use in many other fields of human activity, including children's toys, adult fitness, military and police applications, courier services, and cycle sports.
..Many important details of the bike have 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.