''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) Order ( la, wikt:ordo#Latin, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between Family_(biology), family and Class_(biology), class. In biological classification, the order is a taxonomi ...

, 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 ''Warhammer 40,000'' is a miniature wargame produced by Games Workshop. It is the most popular miniature wargame in the world, and is particularly popular in the United Kingdom. The first edition of the rulebook was published in September 1987, ...

'' has three main ordines: Ordo Malleus, Ordo Hereticus and Ordo Xenos *

Ordo Templi Orientis Ordo Templi Orientis (O.T.O.; ) is an occult Initiation, initiatory organization founded at the beginning of the 20th century. The origins of the O.T.O. can be traced back to the German-speaking occultists Carl Kellner (mystic), Carl Kellner, He ...

, 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 The phrase ''Novus ōrdō sēclōrum'' (, ; "New order of the ages") is the second of two mottos added by the secretary of the Congress of the Confederation, Charles Thomson, on the reverse (the back side) of the Great Seal of the United States ( ...

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 The Catholic Church, also known as the Roman Catholic Church, is the largest Christian church, with 1.3 billion baptized Catholics worldwide . It is among the world's oldest and largest international institutions, and has played a ...

See also