Gamma

Gamma is the third letter of the Greek alphabet. In the system of Greek numerals it has a value of 3. In Ancient Greek, the letter gamma represented a voiced velar stop. In Modern Greek, this letter normally represents a voiced velar fricative, except before either of the two front vowels.
In the International Phonetic Alphabet and other modern Latin-alphabet based phonetic notations, it represents the voiced velar fricative.

History

The Greek letter Gamma Γ is a grapheme derived from the Phoenician letter which was rotated from the right-to-left script of Canaanite to accommodate the Greek language's writing system of left-to-right. The Canaanite grapheme represented the /g/ phoneme in the Canaanite language, and as such is cognate with gimel ג of the Hebrew alphabet.
Based on its name, the letter has been interpreted as an abstract representation of a camel's neck, but this has been criticized as contrived, and it is more likely that the letter is derived from an Egyptian hieroglyph representing a club or throwing stick.
File:NAMA Alphabet grec.jpg|thumb|left|The alphabet on black-figure pottery with a lambda-shaped gamma
In Archaic Greece, the shape of gamma was closer to a classical lambda, while lambda retained the Phoenician L-shape.
Letters that arose from the Greek gamma include Etruscan ?, Roman C and G, Runic kaunan, Gothic geuua, the Coptic Ⲅ, and the Cyrillic letters Г and Ґ.

Greek phoneme

The Ancient Greek /g/ phoneme was the voiced velar stop, continuing the reconstructed proto-Indo-European *g, *ǵ.
The modern Greek phoneme represented by gamma is realized either as a voiced palatal fricative before a front vowel, or as a voiced velar fricative in all other environments. Both in Ancient and in Modern Greek, before other velar consonants, gamma represents a velar nasal. A double gamma γγ represents the sequence or.

Phonetic transcription

Lowercase Greek gamma is used in the Americanist phonetic notation and Uralic Phonetic Alphabet to indicate voiced consonants.
The gamma was also added to the Latin alphabet, as Latin gamma, in the following forms: majuscule Ɣ, minuscule ɣ, and superscript modifier letter ˠ.
In the International Phonetic Alphabet the minuscule letter is used to represent a voiced velar fricative and the superscript modifier letter is used to represent velarization. It is not to be confused with the character, which looks like a lowercase Latin gamma that lies above the baseline rather than crossing, and which represents the close-mid back unrounded vowel. In certain nonstandard variations of the IPA, the uppercase form is used.
It is as a full-fledged majuscule and minuscule letter in the alphabets of some of languages of Africa such as Dagbani, Dinka, Kabye, and Ewe, and Berber languages using the Berber Latin alphabet.
It is sometimes also used in the romanization of Pashto.

Mathematics and science

Lowercase

The lowercase letter is used as a symbol for:

Chromatic number of in graph theory
Gamma radiation in nuclear physics
Shear strain in physics
Surface tension in physics
The photon, the elementary particle of light and other electromagnetic radiation
The 434 nm spectral line in the Balmer series
Surface energy in materials science
The Lorentz factor in the theory of relativity
In mathematics, the lower incomplete gamma function
The heat capacity ratio 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. This always-rare use is deprecated.
A non-SI unit of measure of magnetic flux density, sometimes used in geophysics, equal to 10⁻⁵ gauss, or 1 nanotesla.
The power by which the luminance of an image is increased in gamma correction
In civil and mechanical engineering:
*Specific weight
*The shear rate of a fluid is represented by a lowercase gamma with a dot above it:
*Austenite, 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
Hermite constant
The Euler’s Constant also known as Euler–Mascheroni constant ≈ 0.57721566490153286
Stieltjes constants
Chvátal–Sankoff constants

The lowercase Latin gamma ɣ can also be used in contexts where gamma must not be confused with the letter y, which can occur in some computer typefaces.

Uppercase

The uppercase letter is used as a symbol for:

In mathematics, the 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.
In solid-state physics, the center of the Brillouin zone
Circulation in fluid mechanics
As reflection coefficient in physics and electrical engineering
The tape alphabet of a Turing machine
The Feferman–Schütte ordinal
Congruence subgroups of the modular group of other arithmetic groups
One of the Greeks in mathematical finance
Music

In Medieval music theory, Gamma was the starting note of the musical scale using the Guidonian hand. Paired with the Solfège syllable ut, it became the origin for the word "gamut".