Second-order may refer to:

Mathematics

Second order approximation In science, engineering, and other quantitative disciplines, order of approximation refers to formal or informal expressions for how accurate an approximation is. Usage in science and engineering In formal expressions, the English_numerals#Ord ...

, an approximation that includes quadratic terms *

Second-order arithmetic In mathematical logic, second-order arithmetic is a collection of axiomatic systems that formalize the natural numbers and their subsets. It is an alternative to axiomatic set theory as a foundation of mathematics, foundation for much, but not all, ...

, an axiomatization allowing quantification of sets of numbers * Second-order differential equation, a differential equation in which the highest derivative is the second *

Second-order logic In logic and mathematics, second-order logic is an extension of first-order logic, which itself is an extension of propositional logic. Second-order logic is in turn extended by higher-order logic and type theory. First-order logic quantifies on ...

, an extension of predicate logic * Second-order perturbation, in

perturbation theory In mathematics and applied mathematics, perturbation theory comprises methods for finding an approximate solution to a problem, by starting from the exact solution of a related, simpler problem. A critical feature of the technique is a middle ...

Science and technology

Second-order cybernetics Second-order cybernetics, also known as the cybernetics of cybernetics, is the recursive application of cybernetics to itself and the reflexive practice of cybernetics according to such a critique. It is cybernetics where "the role of the observer ...

, the recursive application of cybernetics to itself and the reflexive practice of cybernetics according to this critique. *

Second-order fluid Second-order may refer to: Mathematics * Second order approximation, an approximation that includes quadratic terms * Second-order arithmetic, an axiomatization allowing quantification of sets of numbers * Second-order differential equation, a di ...

, an extension of fluid dynamics *

Second order Fresnel lens A Fresnel lens ( ; ; or ) is a type of composite compact lens which reduces the amount of material required compared to a conventional lens by dividing the lens into a set of concentric annular sections. The simpler dioptric (purely refractiv ...

, a size of lighthouse lens *

Second-order reaction In chemistry, the rate equation (also known as the rate law or empirical differential rate equation) is an empirical differential mathematical expression for the reaction rate of a given reaction in terms of concentrations of chemical species and ...

, a reaction in which the rate is proportional to the square of a reactant's concentration

Psychology and philosophy

Second-order conditioning In classical conditioning, second-order conditioning or higher-order conditioning is a form of learning in which the first Stimulus (psychology), stimulus is classically conditioned to an unconditioned stimulus, then a second stimulus is classical ...

, a form of learning from previous learning *

Second-order desire Higher-order volitions (or higher-order desire), as opposed to action-determining volitions, are volitions about volitions. Higher-order volitions are potentially more often guided by long-term beliefs and reasoning. A higher-order volition can go ...

, the desire to have a desire for something *

Second-order stimulus Motion perception is the process of inferring the speed and direction of elements in a scene based on visual, vestibular and proprioceptive inputs. Although this process appears straightforward to most observers, it has proven to be a difficult ...

, a visual stimulus distinguished by an aspect other than luminance

Other uses

Second Order (religious) When referring to Roman Catholic religious orders, the term second order refers to those communities of contemplative cloistered nuns which are a part of the religious orders that developed in the Middle Ages. History Dominican In early thirteenth ...

, the cloistered nuns who are affiliated with mendicant orders of friars {{Disambiguation