A bicycle, also known as a bike, pushbike or cycle, is a human-powered,pedal-driven, single-track vehicles, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or 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 bicycle racing.