A circus is a company of performers that may include clowns, acrobats, trained animals, trapeze acts, musicians, hoopers, tightrope walkers, jugglers, unicyclists and other object manipulation and stunt-oriented artists. The term 'circus' also describes the performance which has followed various formats through its 150 year modern history. Philip Astley is credited with being the 'father' of the modern circus when he opened the first circus in 1768 in England. Early circuses were almost exclusively demonstrations of equestrian skills with a few other types of acts to link the horsemanship performances. Performances developed significantly through the next fifty years, with large scale theatrical battle reenactments becoming a significant feature. The 'traditional' format, whereby a ringmaster introduces a varied selection of acts that mostly perform choreographed acts to traditional music, developed in the latter part of 19th century and continued almost universally to be the main style of circus up until the 1970s.
Contemporary circus has been credited with reviving the circus tradition since the 1980s when a number of groups introduced circus based almost solely on human skills and which drew from other performing art skills and styles. As styles of performance have changed since the time of Astley, so too have the types of venues where these circuses have performed. The earliest modern circuses were performed in open air structures with limited covered seating. From the late 18th to late 19th century bespoke circus buildings (often wooden) were built with various types of seating, a centre ring and sometimes a stage. The 'traditional' large tents, commonly known as 'Big Tops' were introduced in the mid 19th century as touring circuses superseded static venues. These tents eventually became the most common venue and remain so to the present day. Contemporary circuses perform in a variety of venues including tents, theatres and casinos. Many circus performances are still held in a ring usually 13 m (42 ft) in diameter. This dimension was adopted by Philip Astley in the late 18th century as the minimum diameter that enabled an acrobatic horse rider to stand upright on a cantering horse to perform their tricks.
First attested in English 14th century, the word circus derives from Latin circus, which is the romanization of the Greek κίρκος (kirkos), itself a metathesis of the Homeric Greek κρίκος (krikos), meaning "circle" or "ring". In the book De Spectaculis early Christian writer Tertullian claimed that the first circus games were staged by the goddess Circe in honor of her father Helios, the Sun God. This claim accords well with the fact that many Roman games were indeed dedicated to the Sun God.
The modern and commonly held idea of a 'circus' is of a Big Top with various acts providing entertainment therein. However, the history of circuses is more complex, with historians disagreeing on its origin, as well as revisions being done about the history due to the changing nature of historical research, and the ongoing 'circus' phenomenon. For many, circus history begins with Astley, while for others its origins go back much further—to Roman times.