A unicycle has one wheel. 

A unicycle has only one wheel. 
Some unicycles are very tall. These are called giraffe unicycles. 
People use them for many things. Some ride in a circus. Others play sports like basketball. 
A unicycle is a vehicle with only one wheel. 
People use unicycles in many ways. Some perform in circuses or street festivals. Others use them for sports. You can play unicycle basketball or unicycle hockey. 

There are many special kinds of unicycles. Giraffe unicycles are very tall. They use a chain to help them work. 
A unicycle is a special vehicle that touches the ground with only one wheel. 

Most unicycles work through a system called direct-drive. This means the pedals are attached to the wheel hub.
People have been riding single wheels for a long time. In 1869, Frederick Myers published a patent for a single-wheeled vehicle. Later, in 1881, Battista Scuri also published a patent. 
There are many different types of unicycles for different paths. Mountain unicycles, or "MUnis," have thick tires for riding on dirt trails. 

Unicycling is a lot like other ways of moving on wheels. It shares parts like pedals, cranks, and saddles with bicycles. However, unicycles usually do not have brakes or gears. This makes them feel very different to ride. Because they lack a frame with two wheels, they can be hard to keep steady. But a skilled rider can be very stable. They can even perform amazing tricks on flat ground or in the streets.
A unicycle, also known as a monocycle, is a unique vehicle that makes contact with the ground using only a single wheel. 
Most standard unicycles operate through a mechanism called direct-drive.
Unicycles are built with specific components to handle different types of movement. The wheel assembly includes a tire, an inner tube, a rim, and spokes. To manage different terrains, riders use specialized types of unicycles. Freestyle unicycles are designed for flatland skills and routines. They often feature a relatively high seatpost and a narrow saddle. Trials unicycles are built to be much stronger than standard models. They must withstand the high stresses caused by jumping and dropping. These models often use wide, knobby tires to help absorb the impact of a landing.
For off-road adventures, riders use mountain unicycles, often called "MUnis." 

History shows that unicycle design has changed significantly over time. The concept for single-wheeled velocipedes was patented by Frederick Myers in 1869. Later, in 1881, Battista Scuri published his own patent for a similar device. 

Unicycling has also become a significant part of organized team sports. Unicycle basketball is played on a regular basketball court using a regulation ball. Players must dribble the ball while riding, and they must be mounted on their unicycles when in-bounding. This sport typically uses 24-inch unicycles or smaller to protect the players and the court. Competitive unicycle basketball teams exist in countries like Switzerland, France, and Puerto Rico. 
When comparing unicycles to other pedal-powered vehicles, there are important mechanical differences. Bicycles, tricycles, and quadracycles share many parts like cranks, forks, and saddles. However, unicycles usually lack brakes, gears, and the ability to freewheel. This lack of a fixed linear axis can actually make a proficient unicyclist more stable than a bicycle rider. Because the mechanics of falling are different, the types of injuries can vary as well. Interestingly, head injuries are significantly less likely during unicycle use compared to bicycle use. This unique combination of physics and skill continues to drive the growth of the sport.
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