A canon is a rule or especially body of rules or principles generally established as valid and fundamental in a field or art or philosophy. A priest who is a member of a cathedral chapter can also be known as canon. Another definition of canon is A ravine formed by a river in an area with little rainfall.
A collection of books accepted as holy scripture especially the books of the Bible recognized by any Christian church as genuine and inspired is also known as canon.
The term Canon derived from the Greek word kanon meaning "rule" is applied in a variety of meanings. A Canon law is an expression is applied for the internal ecclesiastical law which administrates a number of churches, most remarkably the Roman Catholic Church, the Eastern Orthodox Churches and the Anglican Communion of Churches.
The method by which church law is legislated, understood and at times adjusticated differs extensively among these three organizations of churches. In all three civilizations, a canon was originally a rule taken up by a council; these canons shaped the foundation of canon law.
The Apostolic Canons or Ecclesiastical Canons of the Same Holy Apostles basically is a compilation of very old ecclesiastical decrees relating to the administration and discipline of the Early Christian Church, incorporated with the Apostolic Constitutions.