A bicycle is a human-powered, pedal-driven, single-track vehicle with two wheels attached to a frame, one behind the other. A person riding a bicycle is called a cyclist or bicyclist. The bicycle has had a significant impact on human society, both as a mode of transport and for recreation. In many regions of the world, more people rely on the bicycle than on any other motorized vehicle for transportation. Bicycles can be used for fitness, transportation and sport, including artistic cycling. They are also a popular children’s toy and have been adapted for use in a variety of other activities, such as mountain biking, racing and BMX.

The first machines similar to the modern bicycle were built in the early 1800s. Inventors gradually added pedals and made the front wheel much larger than the rear to achieve higher speeds. These early machines were often referred to as hobby horses, boneshakers or velocipedes, but the name bicycle was not adopted until the 1860s.

By the turn of the 20th century, the bicycle had revolutionized both industrial and social life. In the cities, it reduced crowding in inner-city tenements by allowing workers to commute from more spacious dwellings into town; and on farms, it allowed workers to move much faster than horses could, reducing dependence on livestock.

The bicycle has a very low environmental footprint, and it is relatively inexpensive to manufacture. Because of these factors, it is a popular means of transport, and it has significantly reduced the need for oil and other fossil fuels in many regions of the world. It is also a very efficient form of transport, requiring only a small fraction of the energy needed to power an automobile for the same distance.

A bicycle can be customised to suit the rider, with accessories such as handlebars, lights, reflectors and mudguards. It can also be fitted with a basket or a trailer for carrying cargo or passengers. Many families own multiple bikes, and some households even have a bicycle repair shop, so that they can keep their favourite rides in tip-top shape.

In the early 21st century, there were more than 1 billion bicycles worldwide. They are the primary mode of transport for many people, especially in developing countries. Bicycles are also used for sport and exercise, military and police applications, courier services and bicycle racing.

There are a number of different styles of bicycle handling, but the most common is the “clamp” style, where the rider uses his or her feet to apply simultaneous and opposing pressure on the features of the bike. The bottom foot pushes down on the pedal, while the top foot pulls up (see the photo below). There is also a more advanced technique known as the “void” style, where the feet open up to create a space between them.

The International Organization for Standardization has a technical committee that deals with cycles and their components, TC149. It is responsible for defining standards for bicycles, their components and accessories, as well as for bicycle tests and procedures.