''Ordo'' (Latin "order, rank, class") may refer to: * A musical phrase constructed from one or more statements of a

rhythmic mode In medieval music, the rhythmic modes were set patterns of long and short durations (or rhythms). The value of each note is not determined by the form of the written note (as is the case with more recent European musical notation), but rather by i ...

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) An orda (also ordu, ordo, or ordon) or horde was a historical sociopolitical and military structure found on the Eurasian Steppe, usually associated with the Turkic and Mongol peoples. This form of entity can be seen as the regional equivalent ...

, 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 "''Directorium''" is a Latin word denoting a guide. In the later Middle Ages it was specially applied to Catholic liturgical guides for praying the Divine Office and Holy Mass. Early history For example, in the early fifteenth century Clement May ...

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 ''Cryptonomicon'' is a 1999 novel by American author Neal Stephenson, set in two different time periods. One group of characters are World War II-era Allied codebreakers and tactical-deception operatives affiliated with the Government Code and ...

'', 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