Greek kanon / Ancient Greek: κανών, Arabic Qanun / قانون, Hebrew kaneh / קנה, "straight"; a rule, code, standard, or measure; the root meaning in all these languages is "reed" (cf. the Romance-language ancestors of the English word "cane").
The Apostolic Canons or Ecclesiastical Canons of the Same Holy Apostles is a collection of ancient ecclesiastical decrees (eighty-five in the Eastern, fifty in the Western Church) concerning the government and discipline of the Early Christian Church, incorporated with the Apostolic Constitutions which are part of the Ante-Nicene Fathers. In the Fourth century the First Council of Nicaea (325) calls canons the disciplinary measures of the Church: the term canon, κανὠν, means in Greek, a rule. There is a very early distinction between the rules enacted by the Church and the legislative measures taken by the State called leges, Latin for laws.
In the Roman Catholic Church, canon law is the system of laws and legal principles made and enforced by the Church's hierarchical authorities to regulate its external organization and government and to order and direct the activities of Catholics toward the mission of the Church. However, despite the power of the church and its insistence on creating a specific format for the way its members would live their lives, it was often not followed. Powerful and/or wealthy individuals often simply didn't abide by the rules and were allowed to approach family life and marriage how they saw fit. A prime instance of this was shown through annulments granted by the church. The church strongly disregarded and disallowed divorce. However, powerful men could often annul their marriages. This was noteworthy due to the fact that an annulment was very distorting to marriage law and contradicting to the disallowance of divorce. An annulment would not only cease a marriage but rather end the marriage and rule that the marriage was never valid, nor did it ever formally exist. Another potent example of Canon Law not being enforced is in regards to polygyny. Men having multiple wives was outright banned by the Catholic church. However, as seen previously in the example of wealthy and powerful individuals it was allowed. Men (even priests) who were powerful enough were allowed to have multiple wives, concubines, mistresses and could have sex prior to marriage. Despite the aforementioned blatant nonobservance to Canon Law, the codes set in place did shape and provide a code that the majority of the members of the catholic church directly abode and lived their lives according to.
In the Latin Church, positive ecclesiastical laws, based directly or indirectly upon immutable divine law or natural law, derive formal authority in the case of universal laws from the supreme legislator (i.e. the Supreme Pontiff), who possesses the totality of legislative, executive, and judicial power in his person, while particular laws derive formal authority from a legislator inferior to the supreme legislator. The actual subject material of the canons is not just doctrinal or moral in nature, but all-encompassing of the human condition.