Kappa
tenth letter of the Greek alphabet
Kappa ( ; uppercase Κ, lowercase κ or cursive ϰ; Greek: κάππα, káppa) is the tenth letter of the Greek alphabet, representing the voiceless velar plosive IPA: [k] sound in Ancient and Modern Greek. In the system of Greek numerals, Kʹ has a value of 20. It was derived from the Phoenician letter kaph (𐤊). Letters that arose from kappa include the Roman K and Cyrillic К. The uppercase form is identical to the Latin K.
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.
This brief starts where responsible research should: with the source description of “Kappa” as tenth letter of the Greek alphabet. Everything that follows is an evidence route, not borrowed authority.
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Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Jun 20, 2026. The linked authority identifier is Q14401. None of the 0 selected statements returned an explicit reference.
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This entry incorporates text from “Kappa” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.