Bicycle pedal in the context of "Roller chain"

A bicycle, also called a pedal cycle, bike, push-bike or cycle, is a human-powered or motor-assisted, pedal-driven, single-track vehicle, with two wheels attached to a frame, one behind the other. A bicycle rider is called a cyclist, or bicyclist.

The bicycle was introduced in the 19th century in Europe. By the early 21st century, there were more than 1 billion bicycles. Bicycles are the principal means of transport in many regions. They also provide a popular form of recreation, and have been adapted for use as children's toys. Bicycles are used for fitness, military and police applications, courier services, bicycle racing, and artistic cycling.

An electric bicycle, e-bike, electrically assisted pedal cycle, or electrically power assisted cycle is a bicycle with an integrated electric motor used to assist propulsion. Many kinds of e-bikes are available worldwide, but they generally fall into two broad categories: bikes that assist the rider's pedal-power (i.e. pedelecs) and bikes that add a throttle, integrating moped-style functionality. Both retain the ability to be pedaled by the rider and are therefore not electric motorcycles. E-bikes use rechargeable batteries and typically are motor-powered up to 25 to 32 km/h (16 to 20 mph). High-powered varieties can often travel up to or more than 45 km/h (28 mph) depending on the model and riding conditions.

Depending on local laws, many e-bikes (e.g., pedelecs) are legally classified as bicycles rather than mopeds or motorcycles. This exempts them from the more stringent laws regarding the certification and operation of more powerful two-wheelers which are often classed as electric motorcycles, such as licensing and mandatory safety equipment. E-bikes can also be defined separately and treated under distinct electric bicycle laws.

Cycling, also known as bicycling or biking, is the activity of riding a bicycle or other types of pedal-driven human-powered vehicles such as balance bikes, unicycles, tricycles, and quadricycles. Cycling is practised around the world for purposes including transport, recreation, exercise, and competitive sport.

A bicycle chain is a roller chain that transfers power from the pedals to the drive-wheel of a bicycle, thus propelling it. Most bicycle chains are made from plain carbon or alloy steel, but some are nickel-plated to prevent rust, or simply for aesthetics.

The crankset (in the US) or chainset (in the UK) is the component of a bicycle drivetrain that converts the reciprocating motion of the rider's legs into rotational motion used to drive the chain or belt, which in turn drives the rear wheel. It consists of one or more sprockets, also called chainringsor chainwheels, attached to the cranks, also called arms or crankarms, to which the pedals attach. It is connected to the rider by the pedals, to the bicycle frame by the bottom bracket, and to the rear sprocket, cassette, or freewheel via the chain.

A freewheel or overrunning clutch is a device in a transmission that disengages the driveshaft from the driven shaft when the driven shaft rotates faster than the driveshaft. An overdrive is sometimes mistakenly called a freewheel, but is otherwise unrelated.

The condition of a driven shaft spinning faster than its driveshaft exists in most chain-driven bicycles when the rider stops pedaling. In a specialized fixed-gear bicycle (that lacks a freewheel) the rear wheel drives the pedals around.

A balance bike (or run bike) is a bicycle without pedals that learners propel by pushing their feet against the ground. By allowing children to focus on developing their sense of balance and coordination before introducing pedalling, balance bikes enable independent riding more quickly than training wheels.

The bottom bracket on a bicycle connects the crankset (chainset) to the bicycle and allows the crankset to rotate freely. It contains a spindle to which the crankset attaches, and the bearings that allow the spindle and crankset to rotate. The chainrings and pedals attach to the cranks. Bottom bracket bearings fit inside the bottom bracket shell, which connects the seat tube, down tube and chain stays as part of the bicycle frame.

The term "bracket" refers to the tube fittings that are used to hold frame tubes together in lugged steel frames which also form the shell that contains the spindle and bearings; the term is now used for all frames, bracketed or not.