Gamma

Gamma (uppercase Γ, lowercase γ; Γάμμα) is the third letter of the Greek alphabet. In the system of Greek numerals it has a value of 3. It was derived from the Phoenician letter Gimel . Letters that arose from Gamma include the Roman C and G and the Cyrillic letters Ge Г and Ghe Ґ.

Uses

Greek

In isolation

In Modern Greek, it represents either a voiced velar fricative /ɣ/ or a voiced palatal fricative /ʝ/. In Ancient Greek, it represented a voiced velar stop /ɡ/.

Before velars

Before other velars (κ, χ k, kh), it represents a velar nasal /ŋ/ in Modern as well as Ancient Greek. A double gamma γγ represents the sequence /ŋɡ/ (phonetically varying [ŋɡ~ɡ]) or /ŋɣ/.

International Phonetic Alphabet

In the International Phonetic Alphabet, lowercase gamma (ɣ) represents the voiced velar fricative. A lowercase gamma that lies above the baseline rather than crossing it (ɤ) represents the close-mid back unrounded vowel.

Math and science

Lower case

The lower-case letter <math>\gamma </math> is used as a symbol for:

• gamma radiation in nuclear physics
• surface energy in materials science
• the Lorentz factor in theory of relativity
• The heat capacity ratio Cp/Cv in thermodynamics
• The activity coefficient in thermodynamics
• The gyromagnetic ratio in electromagnetism
• gamma oscillation in neuroscience
• Gamma Motor Neurons in neuroscience
• antibiotic concentration (1 <math>\gamma </math> = 1 µg/ml) in microbiology
• 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: <math> \dot \gamma </math>
  • Austenite (also known as γ-iron), a metallic non-magnetic allotrope or solid solution of iron.

Upper case

The upper-case 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 numbers
• 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

See also

• Г, г - Ge (Cyrillic)
• G, g - Latin
• photon