The bicycle is a human-powered, two-wheeled, self-propelled vehicle that was first developed in the 19th century. It is the most efficient means of human-powered transportation, in terms of the amount of energy it takes to travel a given distance. It is also a relatively light and safe form of transport. The bicycle’s design is based on simple principles of geometry and physics, making it easy for almost anyone to learn to ride.

The word “bike” is most commonly used to describe a bicycle with upright seating, but there are many other types of bicycles. For example, there are recumbent bicycles, with a chair-like seat that some people find more comfortable than a saddle, and there are racing bikes, with narrower handlebars and more aggressive frame designs. Regardless of the type of bicycle, most modern bikes have a diamond-shaped frame, with a front fork that connects to the steering arm and to the front wheel, and a rear triangle consisting of paired chain stays and seat tubes.

Some bicycles have hub brakes, with a friction pad that is held in contact with the wheel by a caliper or drum brake. A brake lever mounted on the handlebars is pushed to apply pressure to these brakes, slowing down the wheels and stopping the bike. Hand-operated hub brakes are also common, although they require more skill and control than pedal-actuated brakes.

Bicycles are used for recreation, exercise, transportation, and competition. Cycling is a popular sport, and there are many competitions, both local and international. Some of these include road and track racing, BMX racing, cyclocross, sportives, time trials, and multi-stage races such as the Tour de France and the Vuelta a Espaa. There are also many other cycling events, such as endurance rides and artistic cycling.

There are several health benefits of cycling, including improved cardiovascular fitness and muscular strength. A person’s balance and coordination are also improved by regular riding. In addition, cycling is an excellent low-impact form of aerobic exercise, and it can help to reduce the risk of osteoporosis by preventing bone loss.

In addition to the obvious physical benefits, cycling can be a very social activity. People often ride with friends or family, and there are many clubs and associations that organize group rides and other activities. Some of these are focused on specific interests, such as trail development, road maintenance and improvement, or bicycle racing. Others have broader goals, such as promoting the environmental benefits of cycling or improving public health.

The term cyclist can be confusing, since it can refer to someone who is involved in competitive cycling and training, or to someone who rides a bike for other reasons. To avoid confusion, it is usually best to use the term “biker”, which is more general and includes all kinds of cyclists. However, there are some exceptions to this rule, such as when the context calls for a more specific and technical term. For instance, a review in the New York Review of Books would likely call for the use of the term “cyclist” to distinguish it from other reviews of books.