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in phytosociology, an ecological grouping of plants, between alliance and class Ordo naturalis (natural order), an outdated rank in biology, equivalent to the modern rank of family Order, in medicine, refers to a formal request made by authorized health practitioners to carry out a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 (mathematics), 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,