Kappa

Variant kappa

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

Kappa (/ˈkæpə/;^[1] 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 . 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.
Kappa statistics such as Cohen's kappa and Fleiss' kappa are methods for calculating inter-rater reliability.

Physics

In cosmology, the Einstein gravitational constant is denoted by κ.
In physics, the torsional constant of an oscillator is given by κ.
In physics, the coupling coefficient in magnetostatics is represented by κ.
In physics, the dielectric coefficient is represented by κ.
In fluid dynamics, the von Kármán constant is represented by κ.
In thermodynamics, the compressibility of a compound is given by κ.

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

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

Economics

In macroeconomics, kappa represents the capital-utilization rate.^[2]

Uppercase (Κ)

History

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

Mathematics and statistics

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

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
Preview	Κ		κ		ϰ		Ⲕ		ⲕ
Unicode name	GREEK CAPITAL LETTER KAPPA		GREEK SMALL LETTER KAPPA		GREEK KAPPA SYMBOL		COPTIC CAPITAL LETTER KAPA		COPTIC SMALL LETTER KAPA
Encodings	decimal	hex	dec	hex	dec	hex	dec	hex	dec	hex
Unicode	922	U+039A	954	U+03BA	1008	U+03F0	11412	U+2C94	11413	U+2C95
UTF-8	206 154	CE 9A	206 186	CE BA	207 176	CF B0	226 178 148	E2 B2 94	226 178 149	E2 B2 95
Numeric character reference	Κ	Κ	κ	κ	ϰ	ϰ	Ⲕ	Ⲕ	ⲕ	ⲕ
Named character reference	Κ		κ		ϰ, ϰ
DOS Greek	137	89	161	A1
DOS Greek-2	181	B5	228	E4
Windows 1253	202	CA	234	EA
TeX			\kappa

Mathematical Kappa

Character information
Preview	𝚱		𝛋		𝛞		𝛫		𝜅
Unicode name	MATHEMATICAL BOLD CAPITAL KAPPA		MATHEMATICAL BOLD SMALL KAPPA		MATHEMATICAL BOLD KAPPA SYMBOL		MATHEMATICAL ITALIC CAPITAL KAPPA		MATHEMATICAL ITALIC SMALL KAPPA
Encodings	decimal	hex	dec	hex	dec	hex	dec	hex	dec	hex
Unicode	120497	U+1D6B1	120523	U+1D6CB	120542	U+1D6DE	120555	U+1D6EB	120581	U+1D705
UTF-8	240 157 154 177	F0 9D 9A B1	240 157 155 139	F0 9D 9B 8B	240 157 155 158	F0 9D 9B 9E	240 157 155 171	F0 9D 9B AB	240 157 156 133	F0 9D 9C 85
UTF-16	55349 57009	D835 DEB1	55349 57035	D835 DECB	55349 57054	D835 DEDE	55349 57067	D835 DEEB	55349 57093	D835 DF05
Numeric character reference	𝚱	𝚱	𝛋	𝛋	𝛞	𝛞	𝛫	𝛫	𝜅	𝜅

Character information
Preview	𝜘		𝜥		𝜿		𝝒		𝝟
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
Encodings	decimal	hex	dec	hex	dec	hex	dec	hex	dec	hex
Unicode	120600	U+1D718	120613	U+1D725	120639	U+1D73F	120658	U+1D752	120671	U+1D75F
UTF-8	240 157 156 152	F0 9D 9C 98	240 157 156 165	F0 9D 9C A5	240 157 156 191	F0 9D 9C BF	240 157 157 146	F0 9D 9D 92	240 157 157 159	F0 9D 9D 9F
UTF-16	55349 57112	D835 DF18	55349 57125	D835 DF25	55349 57151	D835 DF3F	55349 57170	D835 DF52	55349 57183	D835 DF5F
Numeric character reference	𝜘	𝜘	𝜥	𝜥	𝜿	𝜿	𝝒	𝝒	𝝟	𝝟

Character information
Preview	𝝹		𝞌		𝞙		𝞳		𝟆
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
Encodings	decimal	hex	dec	hex	dec	hex	dec	hex	dec	hex
Unicode	120697	U+1D779	120716	U+1D78C	120729	U+1D799	120755	U+1D7B3	120774	U+1D7C6
UTF-8	240 157 157 185	F0 9D 9D B9	240 157 158 140	F0 9D 9E 8C	240 157 158 153	F0 9D 9E 99	240 157 158 179	F0 9D 9E B3	240 157 159 134	F0 9D 9F 86
UTF-16	55349 57209	D835 DF79	55349 57228	D835 DF8C	55349 57241	D835 DF99	55349 57267	D835 DFB3	55349 57286	D835 DFC6
Numeric character reference	𝝹	𝝹	𝞌	𝞌	𝞙	𝞙	𝞳	𝞳	𝟆	𝟆

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

↑ "kappa". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
↑ "University of Hong Kong School of Business" (PDF). HKU.

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[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.

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