A circus is a group of many different performers, often including clowns, trapeze artists, and animal trainers. When the circus comes to town, you'll see a big, striped tent being set up for the show.
The ringmaster of a circus has historically been a kind of narrator, calling for the audience's attention and announcing different entertainers. Traditional circuses have performing animals, clowns, and acrobats, while more contemporary circuses combine elements of theater, dance, acrobatics, and music. You can also use circus to mean "noisy, confused activity." In Latin, the word circus means "ring," and the Romans used it to describe the arenas in which performances took place.