# Order

Order, ORDER or Orders may refer to:
* A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
* Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of different ways
* Hierarchy, an arrangement of items that are represented as being "above", "below", or "at the same level as" one another
* an action or inaction that must be obeyed, mandated by someone in authority

## People

* Orders (surname)

## Arts, entertainment, and media

* Order (film), a 2005 Russian film
* Order (album), a 2009 album by Maroon
* "Order", a 2016 song from Brand New Maid by Band-Maid
* Orders (1974 film), a film by Michel Brault
* "Orders" (Star Wars: The Clone Wars)

## Business

* Blanket order, a purchase order to allow multiple delivery dates over a period of time
* Money order or postal order, a financial instrument usually intended for sending money through the mail
* Purchase order, a document issued by a buyer to a seller, indicating types, quantities, and agreed prices
* Sales order, an order issued by a business or trader to a customer

## Exclusive organisations

* Order (distinction), a visible honour in society
** Dynastic order of a presently or formerly sovereign royal house
** National order of a sovereign state
** Order of merit of a state or other entity
** Order of precedence, a sequential hierarchy of the nominal importance of items
* Fraternal order
* Military order (religious society), established in the era of the Crusades
* Order of chivalry, established since the Middle Ages

## Legal and political terminology

* Court order, made by a judge, e.g., a restraining order
* Executive order (disambiguation)
* Law and order (politics), approach focusing on harsher enforcement and penalties as ways to reduce crime
* Public-order crime, type of crime that runs contrary to social order
** Organized crime, groupings of highly centralized criminal enterprises
* Social order, set or system of linked social structures, institutions, relations, customs, values and practices
* Statutory instrument, type of delegated legislation
* Professional order, organization which comprises all the members of the same profession

## Military

* Military order (disambiguation)
* Military order (instruction), binding instruction given by a senior rank to a junior rank in a military context
** General order, a published directive from a commander
** Standing order (disambiguation)
* An order of chivalry, if membership is conferred on military personnel as a result of valorous, exemplary or distinguished service
* Tactical formation, an arrangement or deployment of moving military forces

## Philosophy

* Great order of being, a mediaeval Christian conceptualisation of the physical world
* Order (logic), a property used to characterize logical systems
* Natural order (philosophy), the moral source from which natural law seeks to derive its authority

## Religion

* Ecclesiastical decoration, order or a decoration conferred by a head of a church
* Holy orders, the rite or sacrament in which clergy are ordained
* Monastic order, a religious way of life in which one renounces worldly pursuits to devote oneself fully to spiritual work
* Order of Mass, an outline of a Mass celebration
* Religious order, a community or organization set apart from the general society for devotion to a religious practice
** Religious order (Catholic), a religious order in the context of the Roman Catholic Church
*** Canon regular, or canonical order, a class of religious orders for priests in the Catholic Church

## Science and technology
### Biology and healthcare

* Order (biology), a classification of organisms by rank
** Order, in phytosociology, an ecological grouping of plants, between alliance and class
** Ordo naturalis (natural order), an outdated rank in biology, equivalent to the modern rank of family
* Order, in medicine, refers to a formal request made by authorized health practitioners to carry out a specific clinical action concerning diagnosis or treatment

### Computing

* Order of computation, the computational complexity in the analysis of algorithms
** Big O notation, notation describing limiting behavior
* Z-order, which graphics cover up others on computer screens

### Mathematics

* Order (journal), an academic journal on order theory
* Order, an arrangement of items in sequence
* Order, the result of enumeration of a set of items
* Order, a mathematical structure modeling sequenced items, dealt with in order theory
* Order of hierarchical complexity, quantified by the model of hierarchical complexity, the ordinal complexity of tasks that are addressed
* Ordered set, an ordered structure, in mathematics
* Ordinate in mathematics, the y element of an ordered pair (x, y)
* Partially ordered set
** Complete partial order
* Permutation, the act of arranging all the members of a set into some sequence or order
* Ranking
* Stochastic ordering of random variables or probability distributions

### Physics

* Implicate and explicate order, ontological concepts for quantum theory
* Order and disorder (physics), measured by an order parameter or more generally by entropy
* Order, optics, the category number of lighthouse Fresnel lenses, defining size and focal length
* Topological order in quantum mechanics, an organized quantum state

### Signal processing

* First-order hold, mathematical model of the practical reconstruction of sampled signals
* Modulation order, the number of different symbols that can be sent using a given modulation
* Polynomial order, of a filter transfer function

### Other uses in science and technology

* ORDER (spacecraft), a space debris removal transport satellite
* Order (mouldings), each of a series of recessed arches and supports around a doorway or similar feature
* Classical order, architectonic orders in architecture
* Collation, the ordering of information
** Alphabetical order, the ordering of letters
* Order of reaction, a concept of chemical kinetics
* Spontaneous order, the natural emergence of structure in systems
* Stream order, used to define river networks based on a hierarchy of tributaries