A bicycle is a vehicle that has two wheels and is pedaled by a rider. The word “bike” is derived from the Greek words bi (meaning two) and kuklos (meaning circles).

A bike may be powered by a pedal or a chain. The most popular form of bicycle power transmission is a chain drive, using a sprocket or derailleur to transmit the power from the pedals to the rear wheel. This allows a rider to match the speed of his or her pedaling to changing terrain.

Bicycles come in many different types and sizes, depending on the rider’s height and weight. If you are new to cycling, you should start out with a bike that is comfortable for you and easy to handle. Then, as you become more familiar with the bike, you can upgrade it to suit your needs.

Most bicycles have a frame that is made from steel or aluminum, and a set of bicycle wheels. Some bikes also have a front fork, which is a metal rod that holds the front wheel in place. The fork is designed to keep the front wheel stable when turning.

The fork and the bicycle frame can be made from a variety of materials. Some are made of wood, while others are manufactured from metal or plastic. Some of the most common components of a bicycle include a chainwheel, cranks, pedals and a saddle.

Some bicycles also have brakes. Brakes stop the bicycle by squeezing pads against the wheels. Other brakes are called hand brakes and use levers on the handlebars to control them.

In addition to braking, some bicycles have gears, which allow the rider to adjust the speed of his or her pedaling. Lower gears make pedaling easier but slow the bicycle down, while higher gears make pedaling harder but allow it to go faster.

These changes in pedaling speed are a way for cyclists to conserve energy and avoid overuse injuries. Riding a bicycle can be an excellent low-impact exercise that helps improve strength, balance and coordination. It can also help reduce your risk of falls, fractures and osteoarthritis.

It is important to remember that you should always take breaks when you are riding a bicycle, especially if you are using it for fitness purposes or if you ride for long periods of time. It is best to give yourself at least one full day off each week to allow your body to recover and to prevent injury.

You should also be sure to wear proper safety equipment while cycling, such as a helmet and lights that are visible at all times. It is also important to know your rights when it comes to traffic and pedestrian laws.

The operation of bicycles on public streets, sidewalks and other traffic-controlled areas in Iowa City is governed by the same rules as motor vehicles. Bicyclists must obey traffic signals and stop at red light and stop signs. They must not ride in a lane or across the center line of a roadway. They also must be able to safely stop for cars and trucks that are stopped at intersections or on the roadway.