A professional body of religious persons (monks or nuns) dedicated to a religious mission. Convents and monasteries predate the establishment of religious orders, which began in the 13th century with St. Dominic and St. Francis. The focus of the religious community moved from a building to the mission, which would combine contemplation with ministry (work in the community). Religious orders have their members adopt vows, typically have a hierarchical organization, and have to be founded with the approval of the Pope.

Source: Catholic Encyclopedia