Reciprocity

Reciprocity may refer to:

Reciprocity (Canadian politics), used to describe the concept of 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
Reciprocity (photography), the relationship between the intensity of the light and duration of the exposure that result in identical exposure
Traffic violations reciprocity where non-resident drivers are treated like residents
Reciprocity (Fringe), a 2011 episode of the television series Fringe

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 connotated responses of individuals towards the actions of others
Ethic of reciprocity (the Golden Rule), one should treat others as one would like others to treat oneself
Serial reciprocity, where the benefactor of a gift or service will in turn provide benefits to a third party

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 (network theory), theorem about transfer function of passive networks
Reciprocity in network, measures the tendency of vertex pairs to form mutual connections between each other
Reciprocity of twist and wrench, in screw theory
Reciprocity theorem (disambiguation), several unrelated results
Antenna_(radio)#Reciprocity, in transmitting and receiving

Reciprocity law 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 for algebraic curves
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.