They're not. A circus generally has animals, while a carnival is a smaller version without animals and more games and food.

Carnival masks are usually used for performances such as circus's funfairs etc

the fair, carnivals, circus or haunted houses

I say that a circus has animals, clowns, and acrobats.

A carnival is close to an amusement park because it has rides and attractions.

It may have a freak show, and some really huge carnivals have a circus tent, such as a Big Top.

A circus rose is yellow with orange or red on the tips and outside edges.