Modern western square dance dance, like traditional square dance, is directed by a "caller". In modern western square dance the caller strings together a sequence of individual "square dance calls" to make a figure or sequence. These calls are the building blocks of the choreography that is danced by the individuals – square dancers – in the squares. There are eight people (four pairs of males and females, traditionally) in each square; at a dance there may be many squares. Generally speaking, each of these squares dances independently of each other, with the exception of specialty or "gimmick" dances, where there might be some
Challenge square dance And Left Thru", or notably, "Circulate"). However, Challenge demands that the dancers have precise understanding of the call definitions, and combines and modifies calls in a way that yields more complex interpretations. In addition to the calls which denote a particular dance action, Challenge dancing makes extensive use of "concepts" which denote modifications to calls – either how they are executed or to whom they apply. There are only a few concepts before C1, e.g., the "As Couples" concept in Advanced. Each Challenge level adds about another ten new concepts. As with calls, the number of concepts at C4 is