During the 4th and 5th centuries it was not customary to place monks, as such, on an equal footing with the clergy, nor were they regarded as part of the clerical body until the 10th century. Before this they were distinguished by the name of religiosi or regulares, and afterwards a distinction was carefully made between clerici sceculares, i.e. parish priests, and those who were charged with the care of souls, and clerici regulares, i.e. those belonging to monastic orders. This name was applied to the latter because they were bound to live according to certain rules (regulae). — Riddle, Christian Antiq.