ORCHESTRA. [[Theatrum].]
ORCĪNUS SĔNĀTOR. [[Senatus].]
ORDO is applied to any body of men who form a distinct class in the community, either by possessing distinct privileges, pursuing certain trades or professions, or in any other way. Thus the whole body of sacerdotes at Rome is spoken of as an ordo, and separate ecclesiastical corporations are called by the same title. The libertini and scribae also formed separate ordines. The senate and the equites are also spoken of respectively as the ordo senatorius and ordo equestris, but this name is never applied to the plebes. Accordingly we find the expression, uterque ordo, used without any further explanation to designate the senatorial and equestrian ordines. The senatorial ordo, as the highest, is sometimes distinguished as amplissimus ordo.—The senate in colonies and municipia was called ordo decurionum [[Colonia]], and sometimes simply ordo.—The term ordo is also applied to a company or troop of soldiers, and is used as equivalent to centuria: thus centurions are sometimes called qui ordines duxerunt, and the first centuries in a legion primi ordines. Even the centurions of the first centuries are occasionally called primi ordines.
ORGIA. [[Mysteria].]
ORGYIA (ὀργυιά), a Greek measure of length, derived from the human body, was the distance from extremity to extremity of the outstretched arms, whence the name, from ὀρέγω. It was equal to 6 feet or to 4 cubits, and was 1-100th of the stadium.
ŎRĬCHALCUM, a metallic compound, akin to copper and bronze, which was highly prized by the ancients. It probably denotes brass, with which the ancients became acquainted by fusing zinc ore (cadmium, calamine) with copper, although they appear to have had scarcely any knowledge of zinc as a metal. The word is derived from ὄρος and χαλκός, that is, mountain-bronze.
OSCHOPHŎRIA (ὠσχοφόρια, ὀσχοφόρια), an Attic festival, which, according to some writers, was celebrated in honour of Athena and Dionysus, and according to others in honour of Dionysus and Ariadne. It is said to have been instituted by Theseus. It was a vintage festival, and its name is derived from ὦσχος, ὄσχος, or ὄσχη, a branch of vines with grapes.
Oscillum. (From a Marble in the British Museum.)