gamma

noun gam·ma \ ˈga-mə \

Updated on: 12 Apr 2018

Definition of gamma

1 : the 3rd letter of the Greek alphabet — see Alphabet Table

2 : the degree of contrast of a developed photographic image or of a video image

3 : a unit of magnetic flux density equal to one nanotesla

4 : gamma ray

gamma counter

5 : microgram

See gamma defined for English-language learners

See gamma defined for kids

Recent Examples of gamma from the Web

The craft's gamma-ray spectrometer found telltale hydrogen, which indicated Mars had enormous amounts of ice.

— the washington post, OregonLive.com, "Trump attacks protections for immigrants from 'shithole' countries in Oval Office meeting," 11 Jan. 2018
That means optical, radio-frequency, X-ray and gamma-ray observations can all be correlated with the gravitational data.

— The Economist, "Gravitational-wave astronomy starts in earnest," 16 Oct. 2017
The mission's payload will eventually include a multispectral imager, a magnetometer, and a gamma-ray spectrometer in order to understand Psyche's history.

— david grossman, Popular Mechanics, "NASA Spacecraft to Investigate Strange Asteroid of Metal," 2 Oct. 2017
The love-him-or-loathe him funnyman was the patron saint of every gamma geek who aspired to be an alpha male.

— carrie rickey, Philly.com, "Jerry Lewis, America's funnyman, dies at 91," 20 Aug. 2017
Researchers want to know more about gamma ray bursts to better understand the universe and its origins.

— carrie wells, baltimoresun.com, "University of Maryland scientists observe rare gamma ray burst," 11 Aug. 2017
Currently, there are more than three dozen orbiting telescopes at work, observing the cosmos in multiple wavelengths, including the visible, ultraviolet, x-ray and gamma ray.

— jeffrey kluger, Time, "As Eclipse Watchers Look to the Sky, a New Age of Telescopes Is Dawning," 1 Aug. 2017
If confirmed, the findings would offer the first solid clue as to what caused Earth's first mass extinction—hypothesized to be the result of everything from toxic metals unleashed in the oceans to radiation from a distant gamma-ray burst.

— shannon hall, Scientific American, "Volcanoes May Have Triggered the Last Unexplained Mass Extinction," 24 July 2017
Other options: exploding stars known as supernovae or gamma ray bursts, highly energetic explosions in outer space.

— giorgia guglielmi, Science | AAAS, "This is what it would take to kill all life on Earth," 14 July 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'gamma.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Origin and Etymology of gamma

Middle English, borrowed from Latin, borrowed from Greek gȧmma, borrowed from Phoenician *gaml-, perhaps with the original sense "throwing stick"

NEW! Time Traveler

First Known Use: 15th century

in the meaning defined at sense 1

See Words from the same year

gamma

adjective

Definition of gamma

1 : of, relating to, or being one of three or more closely related chemical substances

2 : third in position in the structure of an organic molecule from a particular group or atom —symbol γ

Recent Examples of gamma from the Web

Sony also adds support for gamma curves, allowing you to correct for different lighting situations while filming and ultimately, a different style for every curve.

— stefan etienne, The Verge, "Sony A7 III and A7R III review: mirrorless magic," 30 Mar. 2018
But black holes produce their own radiation, especially high-energy X-rays and gamma-rays, which shoot out from the star in the form of tightly collimated...

— Newsweek, "Analysis," 14 Mar. 2018
The collective radiation from all of these hydrogen atom collisions, in the form of light, heat, gamma rays, and X-rays, slowly makes its way to the outer layer of a star.

— mike lynch / sky watch, Twin Cities, "Sky Watch: Inside the violent core of a star (and our sun)," 18 Mar. 2017
The machine uses gamma rays to shrink brain tumors as an alternative to open-skull surgery, Andy Marso reports.

— max londberg, kansascity.com, "Morning Rush: Chiefs fire GM John Dorsey, roaches at area food operations, Big Slick," 23 June 2017
World View has since carried other experiments, including a gamma ray detector and a remote-sensing system.

— adam mann, Science | AAAS, "Commercial balloons in the stratosphere could monitor hurricanes and scan for solar storms," 22 June 2017
These are caused by the collapse of a massive star into a black hole or the collision of a pair of the dense stellar remnants called neutron stars, and squirt gamma rays but only in one direction.

— dennis overbye, New York Times, "A Mysterious Flash From a Faraway Galaxy," 31 Mar. 2017
In the 1960s, when gamma-ray bursts were first detected, scientists didn’t know what to make of them.

— National Geographic, "Astronomers Discover a New Kind of Radio Blast From Space," 2 Mar. 2016

Origin and Etymology of gamma

attributive use of ¹gamma

NEW! Time Traveler

First Known Use: 1834

in the meaning defined at sense 1

See Words from the same year

GAMMA Defined for English Language Learners

gamma

noun

Definition of gamma for English Language Learners

: the third letter of the Greek alphabet

Medical Dictionary

gamma

noun gam·ma \ ˈgam-ə \

medical Definition of gamma

1 : the third letter of the Greek alphabet —symbol Γ or γ

2 : a unit of magnetic flux density equal to one nanotesla

3 : gamma ray —usually used as the attributive form of gamma ray

gamma counter

4 : microgram 1

gamma

adjective

variants: or γ-

medical Definition of gamma

1 : of or relating to one of three or more closely related chemical substances

the gamma chain of hemoglobin

γ-yohimbine

—used somewhat arbitrarily to specify ordinal relationship or a particular physical form and especially one that is allotropic, isomeric, or stereoisomeric (as in gamma benzene hexachloride)

2 : third in position in the structure of an organic molecule from a particular group or atom; also : occurring at or having a structure characterized by such a position