canonici was used to denote canon law as legal system beginning in the thirteenth century. Other terms sometimes used synonymously with ius canonicum include ius sacrum, ius ecclesiasticum, ius divinum, and ius pontificium, as well as sacri canones (sacred canons). is the positive law that emanates from the legislative power of the Catholic Church in its effort to govern its members in accordance with the Gospel of Jesus Christ. Fernando della Rocca used the term "ecclesiastical-positive law" in contradistinction to civil-positive law, in order to differentiate between the human legislators of church and state, all of which issue "positive law" in the normal sense. Examples of ecclesiastical positive law are fasting during the liturgical season of Lent, and religious workers (monks, nuns, etc.) requiring permission from their superiors to publish a book. Etymology of "canon" The word "canon" comes from the Greek kanon, which in its original usage denoted a straight rod, was later used for a measuring stick, and eventually came to mean a rule or norm. In 325, when the first ecumenical council, Nicaea I, was held, kanon started to obtain the restricted juridical denotation of a law promulgated by a synod or ecumenical council, as well as that of an individual bishop. Sources of canon law The term source or fountain of canon law (fons iuris canonici) may be taken in a twofold sense: a) as the formal cause of the existence of a law, and in this sense, we speak of the fontes essendi (Latin: "sources of being") of canon law or lawgivers; b) as the material channel through which laws are handed down and made known, and in this sense the sources are styled fontes cognoscendi (Latin: "sources of knowing"), or depositaries, like sources of history. Legal history and codification The Catholic Church has the oldest continuously functioning legal system in the West, much later than Roman law but predating the evolution of modern European civil law traditions. What began with rules ("canons") allegedly adopted by the Apostles at the Council of Jerusalem in the first century has developed into a highly complex legal system encapsulating not just norms of the New Testament, but some elements of the Hebrew (Old Testament), Roman, Visigothic, Saxon, and Celtic legal traditions. As many as 36 collections of canon law are known to have been brought into existence before 1150. The history of Latin canon law can be divided