The bicycle is a human-powered, two-wheeled land vehicle that is used for transport and recreation. It consists of a frame, two wheels, one pedal, and a chain connected to the pedals and to the rear wheel. The bicycle is the most efficient means of human-powered transportation, in terms of the amount of energy that a person must expend to travel a given distance. It is also the safest form of passenger transportation when compared to automobiles and motorcycles. People use bikes for exercise, as a mode of transportation, to haul cargo, for recreational purposes, and in many other ways. A bicycle is a very complex machine, and it is important to understand how a bicycle works before riding one.

The history of the bicycle began in 1868 when Frenchman Baron Georges-Édouard von Grateau introduced the velocipede. This two-wheeled machine was more efficient than walking, but it was difficult to balance and control. Various improvements were made, and by the end of the velocipede craze in America in 1871, the dwarf ordinary had replaced it as the dominant bike. The new design addressed the problems of stability and steering by lowering the front wheel diameter and positioning the seat further back, but it still required a person to both pedal and steer, which was not ideal for long-distance travel. Improvements included a larger rear wheel, a more comfortable saddle, better quality tires and bearings, and standardized parts.

After 1900, there was a boom in bicycle production, and the bike gained popularity worldwide. The most significant technical advancement was multiple-speed gearing. After the invention of hub gears by William Reilly in 1896, and derailleur gears in the 1920s, the bicycle became a very efficient mode of transportation.

A bicycle can be equipped with accessories to make it more comfortable and functional, including a suspension seat post and fork, handlebar grips, and bicycle lights. People may add auxiliary saddles or pegs to the frame to allow additional riders, or they can carry luggage, tools, and other supplies on trailers attached to the rear of the bicycle. People often attach baskets or bags to the handlebars for carrying items, and they may wear a helmet to protect themselves from falls and collisions.

Riding a bicycle requires a great deal of skill and attention to safety. It is possible to perform tricks on a bicycle, such as performing a stoppie or endo, which involves using the rider’s legs to generate enough force to lift the front wheel off the ground while maintaining control and balance on the bicycle. The bicycle’s design allows it to be ridden in an upright position with the feet off the ground, and some cyclists prefer this style of riding. The rider’s knees should be slightly bent to keep the body stable, and it is often helpful to wear padded clothing to prevent injury if the rider falls. Pedals can be equipped with toe clips or clipless pedals that enable the rider to engage and disengage the pedals with ease.