The bicycle is an efficient human-powered vehicle that can travel long distances with little energy expenditure. It can also carry cargo and be used for recreation, sport, or work. Riding a bicycle requires both physical skill and careful consideration of the machine and its surroundings. Many people find the bicycle easy to ride, but riding a fast and safe bicycle takes practice and attention.

There are several variants of the bicycle, including mountain bikes and racing bikes. The bicycle’s frame is made of steel or aluminium, and it may have one or two front wheels, and either a single or double rear wheel. The front wheel usually has a suspension to reduce vibration and increase comfort. The handlebars, seat post and crankset (a set of metal levers that connect the pedals to the chain) are connected by a truss called the diamond frame.

A bicycle’s brakes are operated by a combination of friction and the centrifugal force of the spinning wheels. When the brake levers are squeezed, rubber shoes clamp firmly onto the inner rims of the front and back wheels, converting the wheel’s kinetic energy into heat by rubbing against the rim. The centrifugal force keeps the wheels spinning, but the braking effect diminishes as the wheels slow down.

During the early 1800s, people built simple two-wheeled vehicles with wooden or steel frames and called them dandy horses, hobby horses, boneshakers, and velocipedes. In the 1860s, Frenchman Pierre Lallement conceived the idea of applying pedals to the front wheel, and Englishman J.K. Starley improved the design with his 1885 Rover bicycle, creating the first recognizably modern bicycle.

The bicycle became a popular form of transportation in the 20th century, and is today used in all countries around the world as an inexpensive way to get around town or for touring. Some cyclists travel long distances, and a few have traveled the entire globe.

In urban areas, cyclists compete with automobile drivers for road space. A bicycle can maneuver more quickly than a car through traffic, so it can avoid many delays. Many people use bicycles for transportation to and from work, school, and stores.

Some cities and towns have special bike routes to help with congestion. Other communities encourage biking by providing secure storage and maintenance facilities. In the United States, bicycles are a common mode of transportation for young children.

A bicycle can be adapted for recreational purposes by adding equipment such as lights, reflectors, and racks for carrying luggage. Some bicycles are equipped with fenders to protect the cyclist from splashes of water or dirt.

A specialized small-framed bicycle with wide tires designed for dirt jumping or other stunt competitions. It is sometimes referred to as a BMX bike, though this name is also used for a similar bicycle developed in the 1970s that uses disk brakes. Bicycles can be modified for racing by adjusting the gearing, handlebars, and frame geometry. A bicycle can be adapted for off-road riding by adding knobby tires and a suspension fork. Bicycles can also be modified for work by installing racks to carry tools, parts and supplies.