chancel, primarily that part of the church close to the altar and used by the officiating clergy. In the early churches it was separated from the nave by a low parapet or open railing ( cancellus ), its name being thus derived. San Clemente at Rome has one of the few preserved examples. With the development of the choir, additional space was taken, between the sanctuary and the nave, for the accommodation of the canons and singers. The chancel rail was moved forward, and the entire space became known as the choir, although it is also termed the chancel; there is no strict differentiation in the usage. In the Middle Ages the chancel rail was replaced by lofty choir screens (see rood), especially in English cathedrals and in monastic churches.