Regular

Regular, orderly, following or arranged according to a rule (Lat. regula, whence O.Fr. reule, whence English "rule"), steady, uniform, formally correct. The earliest and only use in English until the 26th century was in the Med. Lat. sense of regularis, one bound by and subject to the rule (regula)  of a monastic or religious order, a member of the "regular" as opposed to the "secular" clergy, and so, as a substantive, a regular, i.e. a monk or friar. Another specific application is to that portion of the armed forces of a nation which are organized on a permanent system, the standing army, as opposed to "irregulars," levies raised on a voluntary basis and disbanded when the particular campaign or war for which they were raised is at an end. In the British army, the forces were divided into regulars, militia and volunteers, until 1906, when they were divided into regular and territorial forces.