Ballet is a specific type of dance. Performances of this dance are called ballets. The female dancers are called ballerinas, the male dancers are called danseur. It is important for ballerinas to have good arches in their feet.
As the child Annika Hansen, Seven of Nine dreamed of one day becoming a ballerina. In 2376, she dismissed this to Chakotay as having been a "juvenile fantasy," but Chakotay commented that "Those are the ones that stick with you." (VOY: "One Small Step")