Look up reciprocal in Wiktionary, the free dictionary.

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