Kappa

Greek proper names and placenames containing kappa are often written in English with "c" due to the Romans' transliterations into the Latin alphabet: Constantinople, Corinth, Crete. All formal modern romanizations of Greek now use the letter "k", however.

The cursive form ϰ is generally a simple font variant of lower-case kappa, but it is encoded separately in Unicode for occasions where it is used as a separate symbol in math and science. In mathematics, the kappa curve is named after this letter; the tangents of this curve were first calculated by Isaac Barrow in the 17th century.

Symbol

Lowercase (κ)

Mathematics and statistics

• In graph theory, the connectivity of a graph is given by κ.
• In differential geometry, the curvature of a curve is given by κ.
• In linear algebra, the condition number of a matrix is given by κ.
• The kappa curve, also known as Gutschoven's curve, is a curve whose shape resembles the letter κ.
• Kappa statistics such as Cohen's kappa and Fleiss' kappa are methods for calculating inter-rater reliability.

Physics

• In cosmology, the Einstein gravitational constant is denoted by κ.
• In physics, the torsional constant of an oscillator is given by κ.
• In physics, the coupling coefficient in magnetostatics is represented by κ.
• In physics, the dielectric coefficient is represented by κ.
• In fluid dynamics, the von Kármán constant is represented by κ.
• thermal conductivity
• In thermodynamics, the compressibility of a compound is given by κ.

Engineering

• In structural engineering, κ is the ratio of the smaller factored moment to the larger factored moment and is used to calculate the critical elastic moment of an unbraced steel member.
• In electrical engineering, κ is the multiplication factor, a function of the R/X ratio of the equivalent power system network, which is used in calculating the peak short-circuit current of a system fault. κ is also used to denote conductivity, the reciprocal of resistivity, rho.

Biology and biomedical science

• In biology, kappa and kappa prime are important nucleotide motifs for a tertiary interaction of group II introns.
• In biology, kappa designates a subtype of an antibody component.
• In pharmacology, kappa represents a type of opioid receptor.

Psychology and psychiatry

• In psychology and psychiatry, kappa represents a measure of diagnostic reliability.

Economics

• In macroeconomics, kappa represents the capital-utilization rate.

Chemistry

• In chemistry, kappa is used to denote the denticity of the compound.

Uppercase (Κ)

History

• In textual criticism, the Byzantine text-type (from Κοινη, Koine, the common text).

Mathematics and statistics

• In set theory, kappa is often used to denote an ordinal that is also a cardinal.

Chemistry

• In pulping, the kappa number represents the amount of an oxidizing agent required for bleaching a pulp.