kappa

Look up Κ or κ in Wiktionary, the free dictionary.

Variant kappa

Greek alphabet
Αα	Alpha	Νν	Nu
Ββ	Beta	Ξξ	Xi
Γγ	Gamma	Οο	Omicron
Δδ	Delta	Ππ	Pi
Εε	Epsilon	Ρρ	Rho
Ζζ	Zeta	Σσς	Sigma
Ηη	Eta	Ττ	Tau
Θθ	Theta	Υυ	Upsilon
Ιι	Iota	Φφ	Phi
Κκ	Kappa	Χχ	Chi
Λλ	Lambda	Ψψ	Psi
Μμ	Mu	Ωω	Omega
Obsolete letters
	Digamma		Qoppa
	San		Sampi
Other characters
	Stigma		Sho
	Heta
Greek diacritics

Kappa (uppercase Κ, lowercase κ or ϰ; Greek: Κάππα) is the 10th letter of the Greek alphabet, used to represent the voiceless velar stop, or "k", sound in Ancient and Modern Greek. In the system of Greek numerals it 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.

Greek proper names and placenames containing kappa are often written in English with "c" due to contemporary rendering into the Latin alphabet by ancient Romans. However, modern transliteration of the Greek language invariably use the letter "k". Compare Κυνοσκεφαλαι, Cynoscephalae (ancient placename); κυνος κεφαλαι, kunos kephalai (phrase), meaning "dog's heads".

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

In mathematics, the kappa curve is named after this letter; the tangents of this curve were first calculated by Barrow (17th Century).

Symbol

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 physics, the torsional constant of an oscillator is given by κ.

In chemistry, the compressibility of a compound is given by κ.

In physics, the Einstein constant of gravitation

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

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 receptors.

Kappa statistics such as Cohen's kappa and Fleiss' kappa are methods for calculating inter-rater agreement.

Upper-case letter Κ is used as a symbol for:

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

In graphical trigonometry, upper-case kappa is used to represent the indefinite cosine of any real radian value. The graphs of y=x and y=cos(x) intersect at the point (K,K). where n is any real radian value and there are an infinite number of cosines. K is approximately equal to 0.739085133215163^{[citation needed]}

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