Reciprocal
# Reciprocal

Reciprocal may refer to:

## In mathematics

* Multiplicative inverse, in mathematics, the number 1/x, which multiplied by x gives the product 1, also known as a reciprocal
* Reciprocal polynomial, a polynomial obtained from another polynomial by reversing its coefficients
* Reciprocal rule, a technique in calculus for calculating derivatives of reciprocal functions
* Reciprocal spiral, a plane curve
* Reciprocal averaging, a statistical technique for aggregating categorical data

## In science and technology

* Reciprocal aircraft heading, 180 degrees (the opposite direction) from a stated heading
* Reciprocal lattice, a basis for the dual space of covectors, in crystallography
* Reciprocal length, a measurement used in science
* Reciprocating engine or piston engine
* Reciprocating oscillation in physical wave theory

### Life sciences and medicine

* Hybrid (biology), in genetics, the result of a reciprocal pair of crossings, forming reciprocal hybrids
* Reciprocal altruism, a form of symbiotic relationship in evolutionary biology
* Reciprocal cross, a breeding experiment in genetics
* Sherrington's law of reciprocal innervation in the theory of muscle activation

### Social sciences

* Reciprocal determinism, a theory in psychology

### Linguistics

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

## In reciprocal relationships

* Reciprocal license, a type of software licenses also known as copyleft
* Reciprocal link between two web pages
* Reciprocal Public License (RPL), a software license
