Gamma

The alphabet on a black figure vessel, with a Λ-shaped gamma

Gamma (uppercase Γ, lowercase γ; Greek: Γάμμα Gámma) is the third letter of the Greek alphabet. In the system of Greek numerals it has a value of 3. In Ancient Greek, gamma represented a voiced velar stop /ɡ/. In Modern Greek, it represents a voiced fricative.

Based on its phonetic value in Modern Greek, gamma has also been introduced in a number of modern Latin-alphabet based phonetic notations (Latin (or latinized) gamma Ɣ).

History

The Greek letter Gamma Γ was derived from the Phoenician letter for the /g/ phoneme (𐤂 gīml), and as such is cognate with Hebrew gimel ג. Based on its name, the letter has been interpreted as an abstract representation of a camel's neck,^[1] but this has been criticized as contrived,^[2] and it is more likely that the letter is derived from an Egyptian hieroglyph representing a club or throwing stick.^[3]

In the archaic period, the shape of gamma was closer to a classical lambda (Λ), while lambda retained the Phoenician L-shape (𐌋).

Letters that arose from the Greek gamma include Etruscan (Old Italic) 𐌂, Roman C and G, Runic kaunan ᚲ, Gothic geuua 𐌲, the Coptic Ⲅ, and the Cyrillic letters Г and Ґ.^[4]

Greek phoneme

The Ancient Greek /g/ phoneme was the voiced velar stop, continuing the PIE voiced velar and palatal stops *g, *ǵ.

The modern Greek phoneme represented by gamma is realized either as a palatal /ʝ/ (before a front vowel, /e, i/), or as a voiced velar fricative /ɣ/ (in all other environments). Both in Ancient and in Modern Greek, before other velars (κ, χ, ξ k, kh, ks), gamma represents a velar nasal /ŋ/. A double gamma γγ represents the sequence /ŋɡ/ (phonetically varying [ŋɡ~ɡ]) or /ŋɣ/.

Phonetic transcription

Lowercase Greek gamma is used in the Americanist phonetic notation and Uralic Phonetic Alphabet to indicate voiced consonants. In International Phonetic Alphabet, it represents the voiced velar fricative.

In these contexts, gamma is considered as an addition to Latin alphabet, the so-called Latin or latinized gamma ɣ (with an upper-case variant Ɣ based on the minuscule).

Latin gamma is used to represent a voiced velar fricative, both in the International Phonetic Alphabet, and in the alphabets of African languages such as Dagbani, Dinka, Kabiyé, and Ewe,^[5] some Berber languages using the Berber Latin alphabet, and sometimes in the romanization of Pashto.

Lowercase Latin gamma is used in the International Phonetic Alphabet to represent the voiced velar fricative. A lowercase Latin gamma that lies above the baseline rather than crossing it (ɤ) represents the close-mid back unrounded vowel. In certain nonstandard variations of the IPA the uppercase form is used.

Mathematics and science

Lower case

The lower-case letter $\gamma$ is used as a symbol for:

• Chromatic number of in graph theory
• Gamma radiation in nuclear physics
• The photon, the elementary particle of light and other electromagnetic radiation
• Surface energy in materials science
• The Lorentz factor in the theory of relativity
• In mathematics, the lower incomplete gamma function
• The heat capacity ratio Cp/Cv in thermodynamics
• The activity coefficient in thermodynamics
• The gyromagnetic ratio in electromagnetism
• Gamma waves in neuroscience
• Gamma motor neurons in neuroscience
• A non-SI metric unit of measure of mass equal to one microgram (1 μg).^[6] This always-rare use is currently deprecated.
• A non-SI unit of measure of magnetic flux density, sometimes used in geophysics, equal to 1 nanotesla (nT).
• The power by which the luminance of an image is increased in gamma correction
• The Euler–Mascheroni constant
• In mechanical engineering:
  • Specific weight
  • The shear rate of a fluid is represented by a lower case gamma with a dot above it: ${\dot \gamma }$
  • Austenite (also known as γ-iron), a metallic non-magnetic allotrope or solid solution of iron.
• The gamma carbon, the third carbon attached to a functional group in organic chemistry and biochemistry; see Alpha and beta carbon

The lowercase Latin gamma ɣ can also be used in contexts (such as chemical or molecule nomenclature) where gamma must not be confused with the letter y, which can occur in some computer typefaces.

Upper case

The upper-case letter $\Gamma$ is used as a symbol for:

• In mathematics, the gamma function (usually written as $\Gamma$-function) is an extension of the factorial to complex numbers
• In mathematics, the upper incomplete gamma function
• The Christoffel symbols in differential geometry
• In probability theory and statistics, the gamma distribution is a two-parameter family of continuous probability distributions.
• Circulation in fluid mechanics
• As reflection coefficient in physics and electrical engineering
• The tape alphabet of a Turing machine
• The Feferman–Schütte ordinal $\Gamma _{0}$

Encoding

HTML

The HTML entities for uppercase and lowercase gamma are Γ and γ.

Unicode

• Greek Gamma

Character	Γ		γ		ᴦ		ᵞ		ᵧ
Unicode name	GREEK CAPITAL LETTER GAMMA		GREEK SMALL LETTER GAMMA		GREEK LETTER SMALL CAPITAL GAMMA		MODIFIER LETTER SMALL GREEK GAMMA		GREEK SUBSCRIPT SMALL LETTER GAMMA
Encodings	decimal	hex	decimal	hex	decimal	hex	decimal	hex	decimal	hex
Unicode	915	U+0393	947	U+03B3	7462	U+1D26	7518	U+1D5E	7527	U+1D67
UTF-8	206 147	CE 93	206 179	CE B3	225 180 166	E1 B4 A6	225 181 158	E1 B5 9E	225 181 167	E1 B5 A7
Numeric character reference	Γ	Γ	γ	γ	ᴦ	ᴦ	ᵞ	ᵞ	ᵧ	ᵧ
Named character reference	Γ		γ

• Coptic Gamma

Character	Ⲅ		ⲅ
Unicode name	COPTIC CAPITAL LETTER GAMMA		COPTIC SMALL LETTER GAMMA
Encodings	decimal	hex	decimal	hex
Unicode	11396	U+2C84	11397	U+2C85
UTF-8	226 178 132	E2 B2 84	226 178 133	E2 B2 85
Numeric character reference	Ⲅ	Ⲅ	ⲅ	ⲅ

• Latin Gamma / phonetic Gamma

Character	Ɣ		ɣ		ˠ		ɤ
Unicode name	LATIN CAPITAL LETTER GAMMA		LATIN SMALL LETTER GAMMA		MODIFIER LETTER SMALL GAMMA		LATIN SMALL LETTER RAMS HORN
Encodings	decimal	hex	decimal	hex	decimal	hex	decimal	hex
Unicode	404	U+0194	611	U+0263	736	U+02E0	612	U+0264
UTF-8	198 148	C6 94	201 163	C9 A3	203 160	CB A0	201 164	C9 A4
Numeric character reference	Ɣ	Ɣ	ɣ	ɣ	ˠ	ˠ	ɤ	ɤ

• CJK Square Gamma

Character	㌏
Unicode name	SQUARE GAMMA
Encodings	decimal	hex
Unicode	13071	U+330F
UTF-8	227 140 143	E3 8C 8F
Numeric character reference	㌏	㌏

• Technical / Mathematical Gamma

Character	ℾ		ℽ		𝚪		𝛄		𝛤		𝛾
Unicode name	DOUBLE-STRUCK CAPITAL GAMMA		DOUBLE-STRUCK SMALL GAMMA		MATHEMATICAL BOLD CAPITAL GAMMA		MATHEMATICAL BOLD SMALL GAMMA		MATHEMATICAL ITALIC CAPITAL GAMMA		MATHEMATICAL ITALIC SMALL GAMMA
Encodings	decimal	hex	decimal	hex	decimal	hex	decimal	hex	decimal	hex	decimal	hex
Unicode	8510	U+213E	8509	U+213D	120490	U+1D6AA	120516	U+1D6C4	120548	U+1D6E4	120574	U+1D6FE
UTF-8	226 132 190	E2 84 BE	226 132 189	E2 84 BD	240 157 154 170	F0 9D 9A AA	240 157 155 132	F0 9D 9B 84	240 157 155 164	F0 9D 9B A4	240 157 155 190	F0 9D 9B BE
UTF-16	8510	213E	8509	213D	55349 57002	D835 DEAA	55349 57028	D835 DEC4	55349 57060	D835 DEE4	55349 57086	D835 DEFE
Numeric character reference	ℾ	ℾ	ℽ	ℽ	𝚪	𝚪	𝛄	𝛄	𝛤	𝛤	𝛾	𝛾

Character	𝜞		𝜸		𝝘		𝝲		𝞒		𝞬
Unicode name	MATHEMATICAL BOLD ITALIC CAPITAL GAMMA		MATHEMATICAL BOLD ITALIC SMALL GAMMA		MATHEMATICAL SANS-SERIF BOLD CAPITAL GAMMA		MATHEMATICAL SANS-SERIF BOLD SMALL GAMMA		MATHEMATICAL SANS-SERIF BOLD ITALIC CAPITAL GAMMA		MATHEMATICAL SANS-SERIF BOLD ITALIC SMALL GAMMA
Encodings	decimal	hex	decimal	hex	decimal	hex	decimal	hex	decimal	hex	decimal	hex
Unicode	120606	U+1D71E	120632	U+1D738	120664	U+1D758	120690	U+1D772	120722	U+1D792	120748	U+1D7AC
UTF-8	240 157 156 158	F0 9D 9C 9E	240 157 156 184	F0 9D 9C B8	240 157 157 152	F0 9D 9D 98	240 157 157 178	F0 9D 9D B2	240 157 158 146	F0 9D 9E 92	240 157 158 172	F0 9D 9E AC
UTF-16	55349 57118	D835 DF1E	55349 57144	D835 DF38	55349 57176	D835 DF58	55349 57202	D835 DF72	55349 57234	D835 DF92	55349 57260	D835 DFAC
Numeric character reference	𝜞	𝜞	𝜸	𝜸	𝝘	𝝘	𝝲	𝝲	𝞒	𝞒	𝞬	𝞬

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.

See also

• Г, г - Ge (Cyrillic)
• G, g - Latin

References

1. Russell, Bertrand (1972). A history of western philosophy (60th print. ed.). New York: Touchstone book. ISBN 9780671314002.
2. Powell, Barry B. (27 March 2009). Writing: Theory and History of the Technology of Civilization. Wiley Blackwell. p. 182. ISBN 978-1405162562.
3. Gordon James Hamilton, The Origins of the West Semitic Alphabet in Egyptian Scripts (2006), 53–56.
4. "Greek Alphabet Symbols". Rapid Tables. Retrieved 25 August 2014.
5. Practical Orthography of African Languages
6. François Cardarelli (2003). Encyclopaedia of Scientific Units, Weights and Measures. Springer-Verlag London Ltd. ISBN 978-1-4471-1122-1.