Kappa (/ˈkæpə/;[1] uppercase Κ, lowercase κ or cursiveϰ; Greek: κάππα, káppa) is the tenth letter of the Greek alphabet, representing the voiceless velar plosiveIPA:[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. Letters that arose from kappa include the Roman K and Cyrillic К. The uppercase form is identical to the Latin K.
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.
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.
U+1D75F𝝟MATHEMATICAL SANS-SERIF BOLD CAPITAL KAPPA
U+1D779𝝹MATHEMATICAL SANS-SERIF BOLD SMALL KAPPA
U+1D78C𝞌MATHEMATICAL SANS-SERIF BOLD KAPPA SYMBOL
U+1D799𝞙MATHEMATICAL SANS-SERIF BOLD ITALIC CAPITAL KAPPA
U+1D7B3𝞳MATHEMATICAL SANS-SERIF BOLD ITALIC SMALL KAPPA
U+1D7C6𝟆MATHEMATICAL SANS-SERIF BOLD ITALIC KAPPA SYMBOL
^The MATHEMATICAL symbols are only used for math. Stylized Greek text should be encoded using the normal Greek letters, with markup and formatting to indicate text style.