What is the meaning of canon?

noun

• A rule or especially body of rules or principles generally established as valid and fundamental in a field or art or philosophy.
  • usage: "the neoclassical canon"; "canons of polite society"
• A priest who is a member of a cathedral chapter.
• A ravine formed by a river in an area with little rainfall.
  • synonyms: canyon
• A contrapuntal piece of music in which a melody in one part is imitated exactly in other parts.
• A complete list of saints that have been recognized by the Roman Catholic Church.
• A collection of books accepted as holy scripture especially the books of the Bible recognized by any Christian church as genuine and inspired. .