Unicycle in the context of Mountain bike trials

A circus is a company of performers who put on diverse entertainment shows that may include clowns, acrobats, trained animals, trapeze acts, musicians, dancers, hoopers, tightrope walkers, jugglers, magicians, ventriloquists, and unicyclists as well as other object manipulation and stunt-oriented artists. The term "circus" also describes the field of performance, training, and community which has followed various formats through its 250-year modern history. Although not the inventor of the medium, Newcastle-under-Lyme born Philip Astley is credited as the father of the modern circus.

In 1768, Astley, a skilled equestrian, began performing exhibitions of trick horse riding in an open field called Ha'penny Hatch on the south side of the Thames River, England. In 1770, he hired acrobats, tightrope walkers, jugglers, and a clown to fill in the pauses between the equestrian demonstrations and thus chanced on the format which was later named a "circus". Performances developed significantly over the next 50 years, with large-scale theatrical battle reenactments becoming a significant feature. The format in which a ringmaster introduces a variety of choreographed acts set to music, often termed "traditional" or "classical" circus, developed in the latter part of the nineteenth century and remained the dominant format until the 1970s.

Bicycle drivetrain systems are used to transmit power on bicycles, tricycles, quadracycles, unicycles, or other human-powered vehicles from the riders to the drive wheels. Most also include some type of a mechanism to convert speed and torque via gear ratios.

Bicycle and motorcycle dynamics is the science of the motion of bicycles and motorcycles and their components, due to the forces acting on them. Dynamics falls under a branch of physics known as classical mechanics. Bike motions of interest include balancing, steering, braking, accelerating, suspension activation, and vibration. The study of these motions began in the late 19th century and continues today.

Bicycles and motorcycles are both single-track vehicles and so their motions have many fundamental attributes in common and are fundamentally different from and more difficult to study than other wheeled vehicles such as dicycles, tricycles, and quadracycles. As with unicycles, bikes lack lateral stability when stationary, and under most circumstances can only remain upright when moving forward. Experimentation and mathematical analysis have shown that a bike stays upright when it is steered to keep its center of mass over its wheels. This steering is usually supplied by a rider, or in certain circumstances, by the bike itself. Several factors, including geometry, mass distribution, and gyroscopic effect all contribute in varying degrees to this self-stability, but long-standing hypotheses and claims that any single effect, such as gyroscopic or trail (the distance between steering axis and ground contact of the front tire), is solely responsible for the stabilizing force have been discredited.

A bicycle tire is a tire that fits on the wheel of a bicycle or similar vehicle. These tires may also be used on tricycles, wheelchairs, and handcycles, frequently for racing. Bicycle tires provide an important source of suspension, generate the lateral forces necessary for balancing and turning, and generate the longitudinal forces necessary for propulsion and braking. Although the use of a pneumatic tire greatly reduces rolling resistance compared to the use of a rigid wheel or solid tire, the tires are still typically the second largest source, after wind resistance (air drag), of power consumption on a level road. The modern detachable pneumatic bicycle tire contributed to the popularity and eventual dominance of the safety bicycle.

Bicycle tires are also used on unicycles, tricycles, quadracycles, tandem bicycles, hand cycles, bicycle trailers, and trailer bikes.

Unicycle hockey is a team sport, similar to rink hockey where players try to hit the ball with their sticks into the other team's goal, except that each player must be mounted on a unicycle to play the ball. A team is composed of five players (plus substitutes), but there is no dedicated goalkeeper role (although one player usually stays back in that position).

The governing body for unicycle hockey is the International Unicycling Federation which publishes the rules for all unicycle sports. The most recent set of rules for unicycle hockey was published in 2019.

Mountain unicycling is an adventure sport that consists of traversing rough terrain on a unicycle. Mountain unicycling (muni or municycling) is undertaken on similar terrain to mountain biking. However, muni requires much more attention to the microfeatures of the short distance in front of the wheel. Unicycles' lack of a freewheel means that descents must be controlled all the way, and the typical lack of a gear system (though two-gear hubs are available) prevents the rider from reaching high speeds. Muni usually takes place on specially designed unicycles, which are equipped with strong hubs, large, knobbly tires, high-grip pedals and rugged frames. Some are also equipped with rim or disc brakes, having the lever mounted under the nose of the saddle. The brake primarily helps to compensate the downhill-slope force, while more expert riders also use it to decelerate or stop.

Muni riders also need a few additional skills than required for either mountain biking or regular unicycling, with core strength, endurance and balance being key.

Numeral or number prefixes are prefixes derived from numerals or occasionally other numbers. In English and many other languages, they are used to coin numerous series of words. For example:

• triangle, quadrilateral, pentagon, hexagon, octagon (shape with 3 sides, 4 sides, 5 sides, 6 sides, 8 sides)
• simplex, duplex (communication in only 1 direction at a time, in 2 directions simultaneously)
• unicycle, bicycle, tricycle (vehicle with 1 wheel, 2 wheels, 3 wheels)
• dyad, triad, tetrad (2 parts, 3 parts, 4 parts)
• twins, triplets, quadruplets (multiple birth of 2 children, 3 children, 4 children)
• biped, quadruped, hexapod (animal with 2 feet, 4 feet, 6 feet)
• September, October, November, December (7th month, 8th month, 9th month, 10th month)
• binary, ternary, octal, decimal, hexadecimal (numbers expressed in base 2, base 3, base 8, base 10, base 16)
• Unary, binary, ternary, quaternary, quinary, senary, septenary, octonary, nonary, denary (related to having a certain number of something—parts, components, elements, divisions, etc.)
• septuagenarian, octogenarian (a person 70–79 years old, 80–89 years old)
• centipede, millipede, myriapod (subgroups of arthropods with numerous feet, suggesting but not implying approximately 100, 1000, and 10000 feet respectively)

In many European languages there are two principal systems, taken from Latin and Greek, each with several subsystems; in addition, Sanskrit occupies a marginal position. There is also an international set of metric prefixes, which are used in the world's standard measurement system.
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