Introduction

World-wide, the vehicle most commonly used for transportation is a utility bicycle. Utility bicycles tend to have a more relaxed geometry, with priority given to the rider's comfort. Most come with components that make commuting by bicycle more practical, such as fenders (also called mudguards in some English speaking regions), racks (for mounting cargo bags or baskets), chainguards, kickstands, bells and generator light systems.

The two most popular types of bicycle in North America, where cycling for recreation is more common, are mountain bikes and road bicycles. They tend to have a more aggressive geometry which requires the rider to bend forward more. To reduce cost and weight, those types are usually sold without the components that make utility bicycles more practical.

The price of a new bicycle can range from US$50 (on sale) to more than US$10,000, depending primarily on the quality, type and weight (the most expensive road bicycles can weigh as little as 6 kg (13 lb)

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 now number over one billion worldwide,providing the principal means of transportation in many regions, notably China and the Netherlands. They are also 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.