CANON - Literally, "a rule. (Gr)" It describes
(1) the inspired Books of the Bible - the Canon of Scripture;
(2) the rules and decrees issued by the early Church (Acts 15:23-29) and by Ecumenical Councils - Canon Law; and
(3) certain parts of worship, such as the Liturgical Canon or the Canon of Matins. A lengthy hymn composed of nine Odes, with each Ode being made up of the Irmos, Troparion, Theotokion and Katabasia. It is a basic element of Matins and may also appear elsewhere.