The bicycle, or bike, is a human-powered, two-wheeled machine that can be used for recreation, transport, and sport. Millions of people use bicycles worldwide to get around, stay healthy, and travel long distances for fun or business. The basic components of all bikes include a seat, pedals, gearing, handlebar, wheels, and brakes, all mounted on a frame. Some bikes also have a horn, lights, and other accessories. Riding a bicycle may seem simple to the uninitiated, but there’s actually a lot of complicated science that goes into getting a person from Point A to Point B on a bike.

In some parts of the world, bicycles are the principal means of transportation, providing a cheap, efficient, and environmentally friendly mode of transport. Bicycles are also popular for recreational riding, including competitive cycling, touring, and leisurely cruising. Many cities and countries have bicycle paths or lanes, and promote cycling as a way to reduce traffic congestion and air pollution.

Cycling is known to have several health benefits, from increasing muscular strength and flexibility to lowering blood pressure and decreasing the risk of depression and heart disease. In addition, it can be a social activity, with groups of friends and family often cycling together, or can provide an opportunity to bond with new acquaintances while enjoying the outdoors and spending time in nature.

Bicycles are relatively simple compared to automobiles, and so they can be maintained by their riders with minimal tools. Many cyclists choose to perform routine maintenance and repair, and some, such as those who commute on their bicycles, do so daily.

There are a wide range of bicycle types and sizes, from compact children’s bicycles to high-performance racing bicycles. The majority of modern bicycles are designed with an aluminum or steel frame, with carbon fiber frames and components being increasingly common for higher-end models. The most common type of tire for a bicycle is the solid-tire, which has a durable tread that attaches to the wheel and stays on it when the rider is sitting or standing on the bicycle.

The bicycle’s pedaling mechanism is highly efficient, both biologically and mechanically, with up to 99% of the energy that a rider puts into the pedals being transferred to the wheel. For this reason, the bicycle is still considered the most efficient human-powered vehicle in terms of the amount of energy that a rider needs to overcome obstacles and travel a given distance. This efficiency is why the bicycle remains such a popular mode of transportation around the world, with more than twice as many bicycles in the world as cars. In some regions, such as the Netherlands, bicycles outnumber automobiles three to one.