Reciprocal may refer to:

In mathematics

Multiplicative inverse In mathematics, a multiplicative inverse or reciprocal for a number ''x'', denoted by 1/''x'' or ''x''−1, is a number which when Multiplication, multiplied by ''x'' yields the multiplicative identity, 1. The multiplicative inverse of a ra ...

, in mathematics, the number 1/''x'', which multiplied by ''x'' gives the product 1, also known as a ''reciprocal'' *

Reciprocal polynomial In algebra, given a polynomial :p(x) = a_0 + a_1x + a_2x^2 + \cdots + a_nx^n, with coefficients from an arbitrary field, its reciprocal polynomial or reflected polynomial,* denoted by or , is the polynomial :p^*(x) = a_n + a_x + \cdots + a_0x^n ...

, a polynomial obtained from another polynomial by reversing its coefficients *

Reciprocal rule In calculus, the reciprocal rule gives the derivative of the reciprocal of a function ''f'' in terms of the derivative of ''f''. The reciprocal rule can be used to show that the power rule holds for negative exponents if it has already be ...

, a technique in calculus for calculating derivatives of reciprocal functions * Reciprocal spiral, a plane curve *

Reciprocal averaging Correspondence analysis (CA) is a multivariate statistical technique proposed by Herman Otto Hartley (Hirschfeld) and later developed by Jean-Paul Benzécri. It is conceptually similar to principal component analysis, but applies to categorical r ...

, a statistical technique for aggregating categorical data

In science and technology

* Reciprocal

aircraft heading In navigation, the heading of a vessel or aircraft is the compass direction in which the craft's bow or nose is pointed. Note that the heading may not necessarily be the direction that the vehicle actually travels, which is known as its '' cours ...

, 180 degrees (the opposite direction) from a stated heading *

Reciprocal lattice Reciprocal lattice is a concept associated with solids with translational symmetry which plays a major role in many areas such as X-ray and electron diffraction as well as the energies of electrons in a solid. It emerges from the Fourier tran ...

, a basis for the dual space of covectors, in crystallography *

Reciprocal length Reciprocal length or inverse length is a quantity or measurement used in several branches of science and mathematics, defined as the reciprocal of length. Common units used for this measurement include the reciprocal metre or inverse metre (symbo ...

, a measurement used in science *

Reciprocating engine A reciprocating engine, more often known as a piston engine, is a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common features of al ...

or piston engine *

Reciprocating oscillation Reciprocating motion, also called reciprocation, is a repetitive up-and-down or back-and-forth linear motion. It is found in a wide range of mechanisms, including reciprocating engines and pumps. The two opposite motions that comprise a single ...

in physical wave theory

Life sciences and medicine

Hybrid (biology) In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different varieties, subspecies, species or genera through sexual reproduction. Generally, it means that each cell has genetic material from two ...

, in genetics, the result of a reciprocal pair of crossings, forming ''reciprocal hybrids'' *

Reciprocal altruism In evolutionary biology, reciprocal altruism is a behaviour whereby an organism acts in a manner that temporarily reduces its fitness while increasing another organism's fitness, with the expectation that the other organism will act in a similar m ...

, a form of symbiotic relationship in evolutionary biology *

Reciprocal cross In genetics, a reciprocal cross is a breeding experiment designed to test the role of parental sex on a given inheritance pattern. All parent organisms must be true breeding to properly carry out such an experiment. In one cross, a male expressin ...

, a breeding experiment in genetics *

Sherrington's law of reciprocal innervation René Descartes (1596–1650) was one of the first to conceive a model of reciprocal innervation (in 1626) as the principle that provides for the control of agonist and antagonist muscles. Reciprocal innervation describes skeletal muscles as exi ...

in the theory of muscle activation

Social sciences

Reciprocal determinism Reciprocal determinism is the theory set forth by psychologist Albert Bandura which states that a person's behavior both influences and is influenced by personal factors and the social environment. Bandura accepts the possibility that an individu ...

, a theory in psychology

Linguistics

Reciprocal construction A reciprocal construction (abbreviated ) is a grammatical pattern in which each of the participants occupies both the role of agent and patient with respect to the other. An example is the English sentence ''John and Mary criticized each othe ...

, a construction in which agent and patient are in a mutual relationship

In reciprocal relationships

Reciprocal license Copyleft is the legal technique of granting certain freedoms over copies of copyrighted works with the requirement that the same rights be preserved in derivative works. In this sense, ''freedoms'' refers to the use of the work for any purpose, ...

, a type of software licenses also known as copyleft *

Reciprocal link In the field of search engine optimization (SEO), link building describes actions aimed at increasing the number and quality of inbound links to a webpage with the goal of increasing the search engine rankings of that page or website. Briefly ...

between two web pages *

Reciprocal obligation In law Law is a set of rules that are created and are enforceable by social or governmental institutions to regulate behavior, with its precise definition a matter of longstanding debate. It has been variously described as a science and a ...

, in law, a type of agreement between two individuals *

Reciprocal Public License The Reciprocal Public License (RPL) is a copyleft software license released in 2001. Version 1.5 of the license was published on July 15, 2007, and was approved by the Open Source Initiative as an open-source license. Description The RPL was a ...