''Ordo'' (Latin "order, rank, class") may refer to: * A musical phrase constructed from one or more statements of a rhythmic mode pattern and ending in a rest *

Big O notation Big ''O'' notation is a mathematical notation that describes the limiting behavior of a function when the argument tends towards a particular value or infinity. Big O is a member of a family of notations invented by Paul Bachmann, Edmund Lan ...

in calculation of algorithm computational complexity * Orda (organization), also ''ordo'' or ''horde'', was a nomadic palace for the Mongol aristocrats and the Turkic rulers * Order (biology), in the taxonomy of organisms * Ordo Recitandi or directorium gives complete details of the celebration of the Eucharist and the Liturgy of the Hours, beginning with the first Sunday of Advent * Religious order in

monasticism Monasticism (from Ancient Greek , , from , , 'alone'), also referred to as monachism, or monkhood, is a religious way of life in which one renounces worldly pursuits to devote oneself fully to spiritual work. Monastic life plays an important role ...

* The Inquisition from '' Warhammer 40,000'' has three main ordines: Ordo Malleus, Ordo Hereticus and Ordo Xenos * Ordo Templi Orientis, an organization dedicated to the religious philosophy of Thelema * The scholarly economic/political science journal ''The ORDO Yearbook of Economic and Social Order'' *

Canderous Ordo The '' Star Wars: Knights of the Old Republic'' series consists of '' Star Wars: Knights of the Old Republic'' and '' Star Wars: Knights of the Old Republic II – The Sith Lords'', with the first game being released in 2003 and set 4,000 year ...

, a fictional character in the Star Wars video games '' Star Wars: Knights of the Old Republic'' and '' Star Wars Knights of the Old Republic II: The Sith Lords'' * A fictional encryption program from the book '' Cryptonomicon'', by Neal Stephenson * Novus ordo seclorum which appears on the reverse of the Great Seal of the United States * Ordo Missae or

Order of Mass Order of Mass is an outline of a Mass celebration, describing how and in what order liturgical texts and rituals are employed to constitute a Mass. The expression Order of Mass is particularly tied to the Roman Rite where the sections under that ...

, the order (regulation) of the Eucharist in the Roman Rite of the Catholic Church

See also