The adjective refers to what is recognized to be authoritative. The Greek word kanon originally referred to a straight reed or rod which is used for measuring length. From this came the idea of a standard, a ruler, or order. Thus, the sixty-six books recognized by the universal Church as inspired Scripture and, therefore, authoritative for life and faith are called "canonical books"̶they are the authoritative books that God gave to His corporate church.
In modern biblical studies one often hear of a subject being considered within "a canonical context." Once the sixty-six books are recognized as canonical, they form a unity. The individual books, while complete on its own, is, nonetheless, part of a larger theological unit. What is says has, therefore, to be understood within this larger context, the "canonical context" receated by all the books of the Bible taken together. Out of this consideration has arisen what is called the "canonical approach," i.e., an approach to doing theology that takes the entire Bible as a unitary work, recognizing that the books of the Bible are not stand-alone works, or even only loosely related, but that they depend on and interfiltrate one another at many levels, both literary and theological.
Both nouns and adjective are also applied to the system of governance in the traditional churches; these canonical rulings require that things, such as the order of priests, the rules of the life and conduct, etc. should conform to certain standards and procedures. The noun is also an honorific for an order of clergy in the Anglican Church. In the Roman Catholic Church, the papal process and decree by which a person is honoured as a saint is known as canonization.
