A bicycle, also known as a pedal cycle or push-bike, is a human-powered, two-wheeled motor vehicle that uses the rider’s feet to move. It is distinguished from a tricycle by having two wheels attached to a frame, one in front of the other, and by having a seat for the rider. Bicycles may have brakes to slow or stop the wheels, and a handlebar for steering. A bicycle can be fitted with a trailer to carry cargo or children.

The first bicycles were made in the early 1880s and had solid rubber tires. Later, John Boyd Dunlop invented the pneumatic tire which greatly improved ride comfort and speed. These improvements led to the development of the modern bicycle, with a frame, chain, and gears that allow the rider to propel himself forward. The bicycle is the most popular form of transportation in the world, and has a large number of applications in sport and recreation, as well as in commerce and trade.

Bicyclists are often stereotyped as uppity, spoilt and weird, although recent research has shown that bike riders actually have lower rates of obesity, heart disease and stroke than people who do not regularly exercise. In addition, it is an excellent form of low-impact exercise.

Many variations are possible on a bicycle, including the addition of mudguards, lights and a basket for carrying groceries. Some have suspension seat posts or saddles to help absorb shock and reduce the strain on the rider’s body. Parents frequently add rear-mounted child seats or a hitch on the frame to tow a trailer to carry cargo or children.

Basic bicycles have a seat, pedals and gearing, and are mounted on a frame. The pedals are connected to the cranks via a chain, and the cranks are attached to the back wheel to make the bicycle move forward. The handlebar is positioned in front of the seat, and turning it swivels the front wheel to steer the bicycle. Some bikes have gearing, which allows the pedals to be turned more slowly or more quickly than the cranks, thus allowing the rider to keep his balance on a steep hill or when stopping suddenly. The most common type of bicycle has three or more gears, and the most advanced bikes have up to 27 gears. Many of the modern bicycles are built with carbon fiber or aluminum alloy frames and components, and can be adjusted to fit the rider’s height and riding style. The gearing can be adjusted manually, or using a derailleur that automatically shifts the chain from one sprocket to another. Some bicycles have an optional electric drive that can be used to assist with climbing steep hills. Most of the newer bicycles have front and rear disc brakes, which provide more stopping power than traditional rim brakes. This is particularly important for women, who are more likely to crash if they try to brake with their hands when descending. This is especially true when wearing heels, as they have a greater tendency to skid than other types of shoes.