Kappa
Kappa (Κ, κ) is the tenth letter of the Greek alphabet. In physics κ is the dielectric constant of a material; in maths it is the curvature of a curve; in statistics it names cumulants.
How to read it
Kappa is said KAP-uh (Cambridge Dictionary: /ˈkæp.ə/ in both British and American English). In Modern Greek κάππα, “Kappa” in the University of Arizona’s guide, is a k sound.
Also searched as: kappa letter, kappa symbol, κ, Κ.
Capital, small and look-alike forms
| Form | Character | Code point | Unicode name |
|---|---|---|---|
| Capital | Κ | U+039A | Greek capital letter kappa |
| Small | κ | U+03BA | Greek small letter kappa |
| Script kappa | ϰ | U+03F0 | Greek kappa symbol |
The capital Κ looks like the Latin K (Cambridge Dictionary gives the symbols K and κ). Unicode encodes a second small form, the script kappa ϰ, which it describes as used as a technical symbol.
Kappa in physics and maths
κ is the dielectric constant. Putting a dielectric between a capacitor’s plates lowers the voltage to V = V₀/κ, and κ, a number greater than 1, is characteristic of the material (OpenStax, University Physics Volume 2). In calculus κ is the curvature of a curve, defined as κ = ‖dT/ds‖, where T is the unit tangent and s the arc length (OpenStax, Calculus Volume 3). In statistics κ stands for cumulants; Jeff Miller’s history of mathematical symbols says R. A. Fisher introduced the notation in 1929.
Write in Greek letters
stringmash.comGreek alphabet translatorWrite English in Greek letters by sound, or turn Greek back into Latin letters as Greek passports do.Read next
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More greek letters
The same shape elsewhere
Browse symbols drawn with letters and numbers.
Sources
- Greek and Coptic: Range 0370–03FF (code chart), The Unicode Standard, Version 18.0, Unicode Consortium, Greek and Coptic, pp. 39–41
- kappa (Cambridge Dictionary entry), Cambridge Advanced Learner’s Dictionary & Thesaurus, Cambridge University Press, kappa, noun
- kappa (American Heritage Dictionary entry), The American Heritage Dictionary of the English Language, Fifth Edition, HarperCollins Publishers, kappa, n.
- Modern Greek Alphabet And Phonetics, University of Arizona, Center for Middle Eastern Studies, Letter table
- University Physics Volume 2, 8.4 Capacitor with a Dielectric, OpenStax (Rice University), Section 8.4
- Calculus Volume 3, 3.3 Arc Length and Curvature, OpenStax (Rice University), Definition of curvature
- Earliest Uses of Symbols in Probability and Statistics, Jeff Miller, Earliest Uses of Various Mathematical Symbols, MacTutor History of Mathematics, University of St Andrews, Notation for parameters and estimates
Researched, edited and approved by Rory Hansen before publishing. Last reviewed September 30, 2026. How we research
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