A canon (from the Latin canonicus, itself derived from the Greek κανονικός, kanonikós, "relating to a rule", "regulary") is a priest or minister who is a member of certain bodies of the Christian clergy subject to an ecclesiastical rule (canon).
Originally, a canon was a cleric living with others in a clergyhouse or, later, in one of the houses within the precinct of or close to a cathedral and ordering his life according to the orders or rules of the church. This way of life grew common (and is first documented) in the eighth century. In the eleventh century, some churches required clergy thus living together to adopt the rule first proposed by Saint Augustine that they renounce private wealth. Those who embraced this change were known as Augustinians or Canons Regular, whilst those who did not were known as secular canons.
Secular canons 
In the Roman Catholic Church, the members of the chapter of a cathedral (cathedral chapter) or of a collegiate church (so called after their chapter) are canons. Depending on the title of the church, several languages use specific titles, e.g., in German Domherr or Domkapitular in a Dom (i.e., cathedral), Stiftsherr in a prelature that has the status of a Stift (notably under a prince of the Church).
One of the functions of the cathedral chapter in the Roman Catholic Church was to elect a Vicar Capitular (now named a Diocesan Administrator) to serve during a sede vacante period of the diocese. Since the 1983 revision of the Code of Canon Law, this responsibility belongs to the college of consultors, unless the national Bishops Conference decides that the functions that canon law ascribes to the college of consultors, including this one, are to be entrusted to the cathedral chapter.
All canons of the Church of England have been secular since the Reformation, although an individual canon may himself also be a member of a religious order. Mostly, however, they are ordained, that is, priests or members of the clergy. Today, the system of canons is retained almost exclusively in connection with cathedral churches. A canon is a member of the chapter of (for the most part) priests, headed by a dean, which is responsible for administering a cathedral or certain other churches that are styled collegiate churches. The dean and chapter are the formal body which has legal responsibility for the cathedral and for electing the (arch)bishop.
Honorary canons 
The title of Canon is still given in many dioceses to senior parish priests (including but not limited to some Area Deans, Rural Deans and their lieutenants and similar) as a largely honorary title. It is usually awarded in recognition of long and dedicated service to the diocese. Honorary canons are members of the chapter in name but are non-residential and receive no emoluments. They are entitled to call themselves canon and have a role in the administration of the cathedral.
Generally speaking, canons in the Anglican Communion are of this sort, and thus are equivalent to a monsignor in the Catholic Church, often wearing the violet or violet-trimmed cassock which is associated with that rank.
Honorary canons within the Catholic Church may still be nominated after the Second Vatican Council. The French Head of State, currently François Hollande, is ex officio the "first honorary canon" of the Archbasilica of St. John Lateran, a title inherited from the Kings of France, who have held it since Henry IV of France. Also, priests (and honorary chaplains) of the Sovereign Military Order of Malta and the Equestrian Order of the Holy Sepulchre are, in fact, honorary canons of these respective Orders and have the right to the honorific title of "Canon" and "Monsignor" in addition to the choir dress of a canon, which includes the mozetta (black with purple piping for Malta and white with a red Jerusalem cross for Holy Sepulchre.)
Lay canons 
In addition to canons who are clerks in holy orders, cathedrals in the Anglican communion may also appoint lay persons as canons. The rank of "lay canon" is especially conferred upon diocesan chancellors (the senior legal officer of the diocese, who is usually, though not exclusively, a lay person).
Since the reign of King Henry IV, the heads of state of France have been granted by the pope the title of sole honorary canon of Saint John Lateran. The proto-canon of the Basilica of St. Mary Major is still the King of Spain.
It has traditionally been said that the King of England (now of the United Kingdom) is a canon or prebendary of St David’s Cathedral, Wales. However, this is based on a misconception. The canonry of St Mary’s College, St David’s became the property of the Crown on the dissolution of the monasteries. The King was never a canon of St David’s, even as a layman. See The Thirty-Nine Articles of Religion (1562) Article 37.
Canon-Professors at Oxford 
Section 2 of the Church of England (Miscellaneous Provisions) Measure 1995 was passed for the express purpose of enabling Christ Church, Oxford, to appoint not more than two lay canons. One of the motivations for this provision was the fact that, under section 6 of the Ecclesiastical Commissioners Act 1840, the position of Regius Professor of Ecclesiastical History in the University of Oxford was annexed to a Residentiary Canonry of the cathedral, meaning that the Regius professorship could be held only by an Anglican priest. Following the death of Peter Hinchliff in 1995 the Regius professorship was held by Henry Mayr-Harting, a Roman Catholic layman, from 1997 until 2003, and was taken up by another lay person, Sarah Foot, in Michaelmas Term 2007. Three other Statutory Professorships, the Regius Professorship of Divinity, Lady Margaret Professorship of Divinity, and Regius Professorship of Moral and Pastoral Theology, are annexed to canonries of Christ Church and must be held by Anglican priests.
Minor canons 
Minor canons are those clergy who are members of the cathedral's establishment and take part in the daily services but are not part of the formal Chapter. These are generally more junior clergy, who in a parish church would be serving a curacy.
Canons regular 
Canons regular are the members of certain religious orders in the Roman Catholic Church (not to be confused with clerics regular), composed of priests and some choir canons who live in community, together in the past with lay brothers. There are a variety of congregations of canons, some of whom are part of the Confederation of Canons Regular of St. Augustine.
- Canons Regular of the Lateran or St. Saviour, who seem to date back to Pope Alexander II (1063)
- Order of the Canons Regular of Premontre; Norbertines founded by St. Norbert (1120)
- Order of the Holy Cross (Canons Regular) founded in Portugal in 1131 and re-founded in 1977
- Canons Regular of the Order of the Holy Cross (the Crosiers), founded at Clair-lieu, near Huy, in Belgium, in 1211
- Swiss Congregation of Canons Regular of Saint Maurice of Agaune
- Gilbertine Order, a solely English order of canons regular, which became extinct under King Henry VIII
- Canons Regular of the Immaculate Conception, a congregation of Canons Regular founded in France in 1871
Many bishops endeavoured to imitate St. Augustine and St. Eusebius, and to live a common life with the clergy of their church. Rules taken from the sacred canons were even drawn up for their use, of which the most celebrated is that of St. Chrodegang, Bishop of Metz (766). In the tenth century, this institution declined; the canons, as the clergy attached to a church and living a common life were called, began to live separately; some of them, however, resisted this relaxation of discipline, and even added poverty to their common life. This is the origin of the canons regular. Pope Benedict XII by his constitution Ad decorem (15 May 1339) prescribed a general reform of the canons regular. The canons regular ex professo united Holy Orders with religious life, and being attached to a church, devoted themselves to promoting the dignity of divine worship. With monks, Holy Orders are incidental and secondary, and are superadded to the religious life. With canons as with the clerks regular, Holy Orders are the principal thing, and the religious life is superadded to the Holy Orders.
See also 
Notes and references 
- Canon 502 §3 of the Code of Canon Law
- Insignia according to Gammarelli and Barbiconi
- "Le président Sarkozy chanoine d'honneur de la basilique Saint-Jean de Latran"
- Liberian Chapter. The Chapter of Saint Mary Major
- Church of England (Miscellaneous Provisions) Measure 1995 No. 2