A unicycle is a pedal vehicle. It is like a bicycle, but it has only one wheel. It has a seat and pedals, but no chain or gears. It is usually used for acting and performing. Unicycles are traditionally more expensive than normal bicycles, because they are far less common.
There are two kind of unicycle; giraffe unicycles and traditional unicycles. Giraffe unicycles are much taller than traditional unicycles, and use a chain so that the performer's legs do not have to stretch very far. Giraffe unicycles are traditionally used by performers in circuses.
Unicycles are often used while the performer is simultaneously juggling or plate spinning. To do this, performers usually rock back and forth on the unicycle. This is called "idling". It lets the performer pay attention to what they are doing in their hands, instead of to the ground in front of them. To "idle" a unicycle, performers usually press one foot down, anchoring it in the bottom position of the wheel. This foot both provides support and completes the rocking motion that is necessary to keep the unicycle balanced.