[ gam-uh ]

  1. the third letter of the Greek alphabet (Γ, γ).

  2. the consonant sound represented by this letter.

  1. the third in a series of items.

  2. Gamma, Astronomy. a star that is usually the third brightest of a constellation: The third brightest star in the Southern Cross is Gamma Crucis.

  3. a unit of weight equal to one microgram.

  4. Physics. a unit of magnetic field strength, equal to 10−5 gauss.

  5. Photography. a measure of the degree of development of a negative or print.

  6. Television. an analogous numerical indication of the degree of contrast between light and dark in the reproduction of an image in television.

  7. Chiefly British. a grade showing that an individual student is in the third, or lowest, of three scholastic sections in a class.: Compare alpha (def. 7), beta (def. 8).

Origin of gamma

From the Greek word gámma

Words Nearby gamma Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use gamma in a sentence

British Dictionary definitions for gamma (1 of 2)


/ (ˈɡæmə) /

  1. the third letter in the Greek alphabet (Γ, γ), a consonant, transliterated as g. When double, it is transcribed and pronounced as ng

  2. the third highest grade or mark, as in an examination

  1. a unit of magnetic field strength equal to 10 –5 oersted. 1 gamma is equivalent to 0.795 775 × 10 –3 ampere per metre

  2. photog television the numerical value of the slope of the characteristic curve of a photographic emulsion or television camera; a measure of the contrast reproduced in a photographic or television image

  3. (modifier)

    • involving or relating to photons of very high energy: a gamma detector

    • relating to one of two or more allotropes or crystal structures of a solid: gamma iron

    • relating to one of two or more isomeric forms of a chemical compound, esp one in which a group is attached to the carbon atom next but one to the atom to which the principal group is attached

Origin of gamma

C14: from Greek; related to Hebrew gīmel third letter of the Hebrew alphabet (probably: camel)

British Dictionary definitions for Gamma (2 of 2)


/ (ˈɡæmə) /

  1. (foll by the genitive case of a specified constellation) the third brightest star in a constellation: Gamma Leonis

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012