A bicycle, also known as a pedal cycle or a push-bike, is a human-powered, two-wheeled vehicle with a frame, a seat, handlebars for steering, and pedals. Bicycles are used for transportation, recreation, and sport. In addition to the basic form, there are many variations, including racing bikes, tandems, and folding bikes. Bicycles are the most efficient means of human-powered transportation in terms of the amount of energy a person must expend to travel a given distance, although the use of gearing may reduce this efficiency by 10-15%.

A bike’s basic components consist of a wheel hub, spokes, and metal or rubber tires. A bicycle’s frame provides a structural basis for the rest of the machine, but it is also designed to accommodate various accessories. The most common is a rack, which can be used to carry groceries or equipment, but it is also possible to mount a basket for carrying goods or a child. The frame may be fitted with a hitch for towing a trailer, or an auxiliary saddle or cargo carrier mounted on the crossbar. A bicycle may be equipped with front and rear reflectors, a bell, or a repair kit.

Bicycles are a great way to see local communities, natural wonders, and agricultural and industrial activity. In addition, they can provide a fun and healthy exercise. Many cities and towns offer bike lanes and paths for safe riding, but it is important to always obey traffic signals and be aware of changing conditions in the street. It is also important to wear a helmet. Head injuries account for 22%-47% of all bike-related deaths, and they are the most frequent cause of long-term disabilities in bike accidents.

In the early 1800s, several improvements were made to make the bicycle easier and safer to ride. One was the safety bicycle, which had a front wheel that was the same size as the back wheel to prevent the rider from being thrown off when stopping. Another was the chain drive, which allowed the cranks to be attached to the frame so that the pedals could be powered directly by the feet instead of having to turn the wheels manually.

Using the pedals to generate power is the most efficient way for humans to move a bicycle, and bicycles are very effective vehicles for carrying loads, since 99% of the energy that is delivered to the pedals is transmitted to the wheels. However, the bicycle is a very complex machine and requires maintenance to keep it in good working order. Bicycles should be examined and maintained regularly, especially after each ride. Keeping the bicycle well-lubricated and tightening loose parts can help prolong the life of the bicycle and ensure that it is operating safely. It is recommended that riders use hand signals to communicate their intentions to other cyclists and motorists, and that they ride in the center of the lane so that drivers can see them. In addition, they should make eye contact with drivers when passing to make sure that the driver understands their intention.