Canons Regular are priests in the Western Church living in community under a rule ("regula" in Latin), and sharing their property in common.
All canons regular are to be distinguished from secular canons who belong to a community of priests attached to a church but do not take vows or live in common under a Rule.
Among canons regular most, but not all, have followed the Rule of St. Augustine and thus have been called Augustinian Canons, known sometimes in English as Austin Canons or Black Canons, from their black habits.
However, one particular group of canons regular who also follow the Rule of St. Augustine are the Premonstratensians or Norbertines, sometimes called in English White Canons, from their white habits.
Canons regular live together in community. The first communities of Canons took vows of common property and stability. As a later development, they now usually take the three vows of chastity, poverty, and obedience though some Orders or congregations of canons regular have retained the vow of stability.
When, in and after the 11th century, the various congregations of Canons Regular were formed, and adopted the Rule of St. Augustine, they were usually called Canonici Regulares Ordinis S. Augustini Congregationis, and in England "Austin Canons" or "Black Canons", but there have always been canons regular who never adopted the Rule of St. Augustine. In a word, canons regular may be considered as the genus, and Austin Canons as the species; or all Austin Canons are canons regular, but not all canons regular are Austin canons.
By 1125 hundreds of communities of Canons had sprung up in Western Europe. Usually they were quite independent of one another, and varied in their ministries. One obvious place where a group of priests was required was within a cathedral, where there were many Masses to celebrate and the Divine Office to be prayed together in community. Canons often came to be associated with cathedrals, but other groups of canons also established themselves in smaller centres.
All the different varieties of canons regular are to be distinguished not only from secular canons but also from:
Writing at a time before the foundation of the mendicant orders (friars), Pope Urban II(died 1099), said there were two forms of religious life: the monastic (like the Benedictines and Cistercians) and the canonical (like the Augustinian Canons). He likened the monks to the role of Mary, and the canons to that of her sister, Martha.