Reciprocity

Reciprocity may refer to:

Law and trade

 * Reciprocity (Canadian politics), free trade with the United States of America
 * Reciprocal trade agreement, entered into in order to reduce (or eliminate) tariffs, quotas and other trade restrictions on items traded between the signatories
 * Interstate reciprocity, recognition of sibling federated states' laws:
 * In the United States specifically:
 * Full Faith and Credit Clause, which provides for it
 * Concealed carry reciprocity
 * Occupational licensing, which in some jurisdictions provides for it
 * Traffic violations reciprocity where non-resident drivers are treated like residents
 * Quid pro quo, a legal concept of the exchange of good or services, each having value

Social sciences and humanities

 * Norm of reciprocity, social norm of in-kind responses to the behavior of others
 * Reciprocity (cultural anthropology), way of defining people's informal exchange of goods and labour
 * Reciprocity (evolution), mechanisms for the evolution of cooperation
 * Reciprocity (international relations), principle that favours, benefits, or penalties that are granted by one state to the citizens or legal entities of another, should be returned in kind
 * Reciprocity (social and political philosophy), concept of reciprocity as in-kind positive or negative responses for the actions of others
 * Reciprocity (social psychology), in-kind positively or negatively connoted responses of individuals towards the actions of others
 * Ethic of reciprocity (the Golden Rule), that one should treat others as one would like others to treat oneself
 * Serial reciprocity, in which the benefactor of a gift or service will in turn provide benefits to a third party

Physical sciences and engineering

 * Reciprocity (engineering), used in the analysis of structures and to resolve complex load conditions
 * Reciprocity (electromagnetism), theorems relating sources and the resulting fields in classical electromagnetism
 * Reciprocity (electrical networks), reciprocity theorem as it relates to current and voltage in electrical networks
 * Reciprocity (network science), measures the tendency of vertex pairs to form mutual connections between each other
 * Reciprocity (optoelectronic), a diode under illumination to the photon emission of the same diode under applied voltage
 * Reciprocity (photography), the relationship between the intensity of the light and duration of the exposure that result in identical exposure
 * Reciprocity of twist and wrench, in screw theory
 * Reciprocity theorem (disambiguation), several unrelated results
 * Reciprocity of antenna transmitting and receiving characteristics
 * Helmholtz reciprocity, linear propagation.

Mathematics

 * Reciprocity law (law of reciprocity) in mathematics, including
 * Quadratic reciprocity, a fundamental result in number theory
 * Cubic reciprocity, theorems that state conditions under which the congruence x3 ≡ p (mod q) is solvable
 * Quartic reciprocity, a collection of theorems in elementary and algebraic number theory that state conditions under which the congruence x4 ≡ p (mod q) is solvable
 * Artin reciprocity law, a general theorem in number theory that provided a partial solution to Hilbert's ninth problem
 * Reciprocity relation or exact differential, a mathematical differential of the form dQ, for some differentiable function Q
 * Weil reciprocity law
 * Reciprocal polynomials, the coefficients of the remainder polynomial are the bits of the CRC
 * Reciprocal square root
 * Reciprocity (projective geometry), a collineation from a projective space onto its dual space, taking points to hyperplanes (and vice versa) and preserving incidence
 * Frobenius reciprocity, from group representation theory
 * Reciprocity law for Dedekind sums
 * Stanley's reciprocity theorem, states that a certain functional equation is satisfied by the generating function of any rational cone and the generating function of the cone's interior
 * Hermite reciprocity for invariants of binary forms.

Other

 * Reciprocity (Fringe), a 2011 episode of the television series Fringe
 * Rural Municipality of Reciprocity No. 32, Saskatchewan, Canada