gamma; Γ, γ +

(Greek: Γ, γ; the third letter of the Greek alphabet; corresponding to g, as in go and as a numeral, it indicates 3)

gamma knife surgery
Radiosurgery in which an intracranial target can be destroyed by ionizing beams of radiation that are directed with stereotaxic precision.

A normal surgical incision is not needed. The therapy is used to treat brain tumors and vascular lesions.

gamma motor neuron
A small nerve originating in the anterior horns of the spinal cord that transmits impulses through type A gamma fibers to intrafusal fibers of the muscle spindle for muscle control.
gamma radiation
Radiation of gamma rays which consist of very high-frequency electromagnetic radiation, similar in nature to X-rays but of shorter wavelength emitted by the nuclei of radioactive substances during decay or by the interactions of high-energy electrons with matter.

Gamma emission usually occurs as part of alpha or beta emissions; however, they are less ionizing in their effect than alpha and beta particles, but are dangerous nevertheless because they can penetrate deeply into body tissues; such as, bone marrow.

Controlled application of gamma radiation is important in the diagnosis and treatment of various conditions, including skin cancer and malignancies deep within the body.

Gamma radiation is also used to kill bacteria and other micro-organisms, to sterilize medical devices, and to change the molecular structure of plastics to modify their properties.

gamma ray, gamma rays
1. A type of emission from radioactive substances, consisting of electromagnetic radiation of great penetrating power and of wavelengths lying beyond the region of the shortest X-rays.
2. A high-energy photon, especially as emitted by a nucleus in a transition between two energy levels.
gamma test
A test using a strip of film to determine the degree of density in a photographic image in comparison with the degree of illumination of the object photographed.
A defect of speech, occurring mostly in younger children, in which the sounds represented by g and k are not articulated, being replaced by other sounds; usually, those which are represented by d.

It results in the "baby talk" of young children.

gammadion, gammation, tetra-gammadion
1. A cross made of four capital gammas; a swastika; a fylfot (a decorative or religious symbol in the form of a swastika).
2. A Greek cross formed of four capital gammas all facing outward so that the ends of the arms of the cross are open.
3. A pattern consisting of four capital Greek gammas (tetra-gammadion); especially, when joined at the center to form a swastika or a very old symbol used by many ancient cultures.

An Example of a Gammadion or a Gammation Symbol

A gammadion symbol or a Greek cross formed of four capital gammas all facing outward.
Any nuclide that emits gamma photons.
gamma-ray altimeter
An altimeter, used at altitudes under several hundred feet, that measures the photon back-scatter from the earth resulting from the transmission of photons to earth from a cobalt-60 gamma source.
gamma-ray astronomy
The study of gamma rays from extraterrestrial sources, especially gamma-ray bursts.

Gamma-ray astronomy is the study of astronomical objects by analysis of the most energetic electromagnetic radiation they emit.

Gamma rays are shorter in wavelength and hence more energetic than X-rays, but much harder to detect and to pinpoint.

X-rays and some gamma rays are produced throughout the universe by the same catastrophic astrophysical events; such as, supernovas and black holes, and gamma-ray astronomy can be considered an extension of X-ray astronomy to the extreme shortwave end of the spectrum.

gamma-ray bursts
Intense blasts of soft gamma rays of unknown origin, which range in duration from a tenth of a second to tens of seconds and occur several times a year from sources widely distributed over the sky.
gamma-ray detector
An instrument used on ships to identify and measure abnormal concentrations of gamma rays in the oceans.
gamma-ray level indicator
A level indicator in which the rising level of the liquid or other material reduces the amount of radiation passing from a gamma-ray source through the container to a Geiger counter or other radiation detector.
gamma-ray probe
A gamma-ray counter built into a watertight case small enough to be lowered into a borehole.
gamma-ray source
A quantity of radioactive material that emits gamma radiation and is in a form that is convenient for radiology.

You can see all of the letters of the Greek Alphabet on this page.