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{{About|the Greek letter Gamma ''Γ'' (and ''γ'') as used in various fields.  For the Latin forms like ''Ɣ'' see {{section link|Gamma|Phonetic transcription}} | other uses|}}
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{{Greek Alphabet|letter=gamma}}
[[File:NAMA Alphabet grec.jpg|thumb|The alphabet on [[black-figure pottery]] with a [[lambda]]-shaped gamma]]

'''Gamma''' {{IPAc-en|'|g|æ|m|ə}}<ref>{{OED|gamma}}</ref> (uppercase {{Script|Grek|Γ}}, lowercase  {{Script|Grek|γ}}; {{Lang-el|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]], the letter gamma represented a [[voiced velar stop]] {{IPA|/ɡ/}}. In [[Modern Greek]], this letter represents either a [[voiced velar fricative]] or a [[Voiced palatal fricative#Palatal|voiced palatal fricative]].

In the [[International Phonetic Alphabet]] and other modern Latin-alphabet based [[phonetic transcription#Alphabetic|phonetic notations]], it represents the voiced velar fricative.

==History==
{{further|History of the Greek alphabet}}
The Greek letter Gamma Γ was derived from the [[Phoenician alphabet|Phoenician letter]] for the /g/ phoneme ({{Script|Phnx|𐤂}} ''gīml''), and as such is cognate with [[Hebrew alphabet|Hebrew]] ''[[gimel]]'' ג.

Based on its name, the letter has been interpreted as an abstract representation of a [[camel]]'s neck,<ref>{{cite book|last=Russell|first=Bertrand|title=A history of western philosophy|year=1972|publisher=Touchstone book|location=New York|isbn=9780671314002|edition=60th print.|url-access=registration|url=https://archive.org/details/historyofwestern00russ}}</ref> but this has been criticized as contrived,<ref>{{cite book|last=Powell|first=Barry B.|authorlink=Barry B. Powell|title=Writing: Theory and History of the Technology of Civilization|url=https://books.google.com/books?id=PZ2Gr3d9X2UC&pg=PA182|year=2012|publisher=John Wiley & Sons|isbn=978-1-118-29349-2|page=182}}</ref> and it is more likely that the letter is derived from an Egyptian hieroglyph representing a club or [[throwing stick]].<ref>{{cite book|last=Hamilton|first=Gordon James|title=The Origins of the West Semitic Alphabet in Egyptian Scripts|url=https://books.google.com/books?id=LdANAAAAYAAJ|year=2006|publisher=Catholic Biblical Association of America|isbn=978-0-915170-40-1|pages=53–6}}</ref>

In [[Archaic Greece]], the shape of gamma was closer to a classical [[lambda]] (Λ), while lambda retained the Phoenician [[L]]-shape ({{Script|Phnx|𐌋}}).

Letters that arose from the Greek gamma include [[Old Italic script#Etruscan alphabet|Etruscan (Old Italic)]] 𐌂,  [[Latin alphabet|Roman]] [[C]] and [[G]], [[Elder Futhark|Runic]] ''[[kaunan]]'' {{Script|Runr|ᚲ}}, [[Gothic alphabet|Gothic]] ''geuua'' {{Script|Goth|𐌲}}, the [[Coptic alphabet|Coptic]] Ⲅ, and the [[Cyrillic script|Cyrillic]] letters [[Ge (Cyrillic)|Г]] and [[Ge with upturn|Ґ]].<ref name="rapidtables">{{cite web | url=http://www.rapidtables.com/math/symbols/greek_alphabet.htm | title=Greek Alphabet Symbols | publisher=Rapid Tables | accessdate=25 August 2014}}</ref>

==Greek phoneme==
{{further|Ancient Greek phonology|Modern Greek phonology}}

The Ancient Greek /g/ phoneme was the voiced velar stop, continuing the reconstructed [[Proto-Indo-European phonology|proto-Indo-European]] ''*g'', ''*ǵ''.

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

==Phonetic transcription==
Lowercase Greek gamma is used in the [[Americanist phonetic notation]] and [[Orenstian 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 {{IPA|ɤ}}, which looks like a lowercase Latin gamma that lies above the [[baseline (typography)|baseline]] rather than crossing, and which represents the [[close-mid back unrounded vowel]]. In certain [[Obsolete and nonstandard symbols in the International Phonetic Alphabet|nonstandard variations of the IPA]], the uppercase form is used.{{Citation needed|date=May 2017}}

It is as a full-fledged majuscule and minuscule letter in the alphabets of some of [[languages of Africa]] such as [[Dagbani language|Dagbani]], [[Dinka language|Dinka]], [[Kabye language|Kabye]], and [[Ewe language|Ewe]],<ref>[http://www.bisharat.net/Documents/poal30.htm Practical Orthography of African Languages]</ref> 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 <math>\gamma</math> is used as a symbol for:
*[[Chromatic number]] of in [[graph theory]]
*[[Gamma ray|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 [[Incomplete gamma function|lower incomplete gamma function]]
*The [[heat capacity ratio]] C<sub>p</sub>/C<sub>v</sub> in [[thermodynamics]]
*The [[activity coefficient]] in [[thermodynamics]]
*The [[gyromagnetic ratio]] in [[electromagnetism]]
*[[Gamma wave]]s in [[neuroscience]]
*[[Gamma motor neuron]]s in [[neuroscience]]
*A non-[[International System of Units|SI]] [[metric system|metric]] [[units of measurement|unit of measure]] of [[mass]] equal to one [[micro-|micro]][[gram]] (1 μg).<ref>François Cardarelli (2003). Encyclopaedia of Scientific Units, Weights and Measures. Springer-Verlag London Ltd. {{ISBN|978-1-4471-1122-1}}.</ref> This always-rare use is currently deprecated.
*A non-[[International System of Units|SI]] [[units of measurement|unit of measure]] of [[magnetic field|magnetic flux density]], sometimes used in [[geophysics]], equal to 1 [[nano-|nano]][[tesla (unit)|tesla]] (nT).{{fact|date=May 2020}}
*The power by which the luminance of an image is increased in [[gamma correction]]
*The [[Euler–Mascheroni constant]]
*In civil and mechanical engineering:
**[[Specific weight]]
**The [[shear rate]] of a fluid is represented by a lowercase gamma with a dot above it: <math> \dot \gamma </math>
**[[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.

===Uppercase===
The uppercase letter <math>\Gamma</math> is used as a symbol for:
*In mathematics, the [[gamma function]] (usually written as <math>\Gamma</math>-function) is an extension of the [[factorial]] to [[complex number]]s
*In mathematics, the [[Incomplete gamma function|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 (fluid dynamics)|Circulation]] in [[fluid mechanics]]
*As [[reflection coefficient]] in physics and electrical engineering
*The tape alphabet of a [[Turing machine]]
*The [[Feferman–Schütte ordinal]] <math>\Gamma_0</math>
*One of the [[Greeks (finance)|Greeks in mathematical finance]]

==Encoding==

===HTML===
The [[List of XML and HTML character entity references#Character entity references in HTML|HTML entities]] for uppercase and lowercase gamma are <code>&amp;Gamma;</code> and <code>&amp;gamma;</code>.

===Unicode===

* Greek Gamma

{{charmap
|0393|name1=Greek Capital Letter Gamma
|03B3|name2=Greek Small Letter Gamma
|1D26|name3=Greek Letter Small Capital Gamma
|1D5E|name4=Modifier Letter Small Greek Gamma
|1D67|name5=Greek Subscript Small Letter Gamma
}}

* Coptic Gamma

{{charmap
|2C84|name1=Coptic Capital Letter Gamma
|2C85|name2=Coptic Small Letter Gamma
}}

* [[Latin Gamma]] / [[International Phonetic Alphabet|phonetic Gamma]]

{{charmap
|0194|name1=Latin Capital Letter Gamma
|0263|name2=Latin Small Letter Gamma
|02E0|name3=Modifier Letter Small Gamma
|0264|name4=Latin Small Letter Rams Horn
}}

* CJK Square Gamma

{{charmap
|330F|name1=Square Gamma
}}

* Technical / Mathematical Gamma

{{charmap
|213E|name1=Double-Struck<br />Capital Gamma
|213D|name2=Double-Struck<br />Small Gamma
|1D6AA|name3=Mathematical Bold<br />Capital Gamma
|1D6C4|name4=Mathematical Bold<br />Small Gamma
|1D6E4|name5=Mathematical Italic<br />Capital Gamma
|1D6FE|name6=Mathematical Italic<br />Small Gamma
}}

{{charmap
|1D71E|name1=Mathematical Bold Italic<br />Capital Gamma
|1D738|name2=Mathematical Bold Italic<br />Small Gamma
|1D758|name3=Mathematical Sans-Serif<br />Bold Capital Gamma
|1D772|name4=Mathematical Sans-Serif<br />Bold Small Gamma
|1D792|name5=Mathematical Sans-Serif<br />Bold Italic Capital Gamma
|1D7AC|name6=Mathematical Sans-Serif<br />Bold Italic Small Gamma
}}

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==
{{Wiktionary|Γ|γ}}
{{Wiktionary|Ɣ|ɣ}}
*[[Ge (Cyrillic)|Г, г - Ge (Cyrillic)]]
*[[G|G, g - Latin]]

==References==
{{reflist}}

[[Category:Greek letters]]
[[Category:Phonetic transcription symbols|Gz]]