The cassock, or soutane, is an item of Christian clerical clothing used by the clergy of Roman Catholic, Eastern Orthodox, Anglican and Reformed churches, among others. "Ankle-length garment" is the literal meaning of the corresponding Latin term, vestis talaris. It is related to habit traditionally worn by nuns, monks, and friars.
The cassock derives historically from the tunic that in ancient Rome was worn underneath the toga and the chiton that was worn beneath the himation in ancient Greece. In religious services, it has traditionally been worn underneath vestments, such as the alb.
In the West, the cassock is little used today except for religious services; but in many countries it was the normal everyday wear of the clergy until the second half of the 20th century, when it was replaced even in those countries by a conventional suit, distinguished from lay dress by being generally black and by incorporating a clerical collar.