Kappa

Kappa /ˈkæpə/[1] (uppercase Κ, lowercase κ or cursive ϰ; Greek: κάππα, káppa) is the 10th letter of the Greek alphabet, representing the voiceless velar plosive IPA: [k] sound in Ancient and Modern Greek. In the system of Greek numerals, has a value of 20. It was derived from the Phoenician letter kaph . Letters that arose from kappa include the Roman K and Cyrillic К. The uppercase form is identical to the Latin K.

Variant kappa
Greek word καί written with a handwritten variant of kappa, from the Byzantine period

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.
  • Kappa statistics such as Cohen's kappa and Fleiss' kappa are methods for calculating inter-rater reliability.
Physics
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
Economics

Uppercase (Κ)

History
  • In textual criticism, the Byzantine text-type (from Κοινη, Koine, the common text).
Mathematics and statistics
Chemistry
  • In chemistry, kappa is used to denote the denticity of the compound.
  • In pulping, the kappa number represents the amount of an oxidizing agent required for bleaching a pulp.

Character encodings

Character information
PreviewΚκϰ
Unicode name GREEK CAPITAL LETTER KAPPA GREEK SMALL LETTER KAPPA GREEK KAPPA SYMBOL COPTIC CAPITAL LETTER KAPA COPTIC SMALL LETTER KAPA
Encodingsdecimalhexdechexdechexdechexdechex
Unicode922U+039A954U+03BA1008U+03F011412U+2C9411413U+2C95
UTF-8206 154CE 9A206 186CE BA207 176CF B0226 178 148E2 B2 94226 178 149E2 B2 95
Numeric character referenceΚΚκκϰϰⲔⲔⲕⲕ
Named character referenceΚκϰ, ϰ
DOS Greek13789161A1
DOS Greek-2181B5228E4
Windows 1253202CA234EA
TeX\kappa
  • Mathematical Kappa
Character information
Preview𝚱𝛋𝛞𝛫𝜅
Unicode name MATHEMATICAL BOLD
CAPITAL KAPPA
MATHEMATICAL BOLD
SMALL KAPPA
MATHEMATICAL BOLD
KAPPA SYMBOL
MATHEMATICAL ITALIC
CAPITAL KAPPA
MATHEMATICAL ITALIC
SMALL KAPPA
Encodingsdecimalhexdechexdechexdechexdechex
Unicode120497U+1D6B1120523U+1D6CB120542U+1D6DE120555U+1D6EB120581U+1D705
UTF-8240 157 154 177F0 9D 9A B1240 157 155 139F0 9D 9B 8B240 157 155 158F0 9D 9B 9E240 157 155 171F0 9D 9B AB240 157 156 133F0 9D 9C 85
UTF-1655349 57009D835 DEB155349 57035D835 DECB55349 57054D835 DEDE55349 57067D835 DEEB55349 57093D835 DF05
Numeric character reference𝚱𝚱𝛋𝛋𝛞𝛞𝛫𝛫𝜅𝜅
Character information
Preview𝜘𝜥𝜿𝝒𝝟
Unicode name MATHEMATICAL ITALIC
KAPPA SYMBOL
MATHEMATICAL BOLD ITALIC
CAPITAL KAPPA
MATHEMATICAL BOLD ITALIC
SMALL KAPPA
MATHEMATICAL BOLD ITALIC
KAPPA SYMBOL
MATHEMATICAL SANS-SERIF
BOLD CAPITAL KAPPA
Encodingsdecimalhexdechexdechexdechexdechex
Unicode120600U+1D718120613U+1D725120639U+1D73F120658U+1D752120671U+1D75F
UTF-8240 157 156 152F0 9D 9C 98240 157 156 165F0 9D 9C A5240 157 156 191F0 9D 9C BF240 157 157 146F0 9D 9D 92240 157 157 159F0 9D 9D 9F
UTF-1655349 57112D835 DF1855349 57125D835 DF2555349 57151D835 DF3F55349 57170D835 DF5255349 57183D835 DF5F
Numeric character reference𝜘𝜘𝜥𝜥𝜿𝜿𝝒𝝒𝝟𝝟
Character information
Preview𝝹𝞌𝞙𝞳𝟆
Unicode name MATHEMATICAL SANS-SERIF
BOLD SMALL KAPPA
MATHEMATICAL SANS-SERIF
BOLD KAPPA SYMBOL
MATHEMATICAL SANS-SERIF
BOLD ITALIC CAPITAL KAPPA
MATHEMATICAL SANS-SERIF
BOLD ITALIC SMALL KAPPA
MATHEMATICAL SANS-SERIF
BOLD ITALIC KAPPA SYMBOL
Encodingsdecimalhexdechexdechexdechexdechex
Unicode120697U+1D779120716U+1D78C120729U+1D799120755U+1D7B3120774U+1D7C6
UTF-8240 157 157 185F0 9D 9D B9240 157 158 140F0 9D 9E 8C240 157 158 153F0 9D 9E 99240 157 158 179F0 9D 9E B3240 157 159 134F0 9D 9F 86
UTF-1655349 57209D835 DF7955349 57228D835 DF8C55349 57241D835 DF9955349 57267D835 DFB355349 57286D835 DFC6
Numeric character reference𝝹𝝹𝞌𝞌𝞙𝞙𝞳𝞳𝟆𝟆

These characters are used only as mathematical symbols. Stylized Greek text should be encoded using the normal Greek letters, with markup and formatting to indicate text style.

References

  1. "kappa". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  2. "University of Hong Kong School of Business" (PDF). HKU.{{cite web}}: CS1 maint: url-status (link)
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