Gamma Photon - Electromagnetic radiation originating from the nuclei of decaying atoms.

GB - Sarin. A nerve agent.

GD - Soman. A nerve agent.

Geiger Counter - An instrument used for detecting radiation.

Genome - The complete set of hereditary factors, as contained in the haploid assortment of chromosomes.

Gram-stain - divides most bacteria into two groups. The gram-reaction depends on the ability of certain bacteria (Gram-positive) to retain a complex of a purple dye and iodine when briefly washed with alcohol. Gram-positive bacteria protect their membrane with a thick cell wall made of peptidoglycan. Gram-negative bacteria do not retain the dye and can be counterstained red.

H - Mustard. A blister agent.

Half Life - The time in which half the atoms of a particular radioactive substance disintegrate to another nuclear form.

HAZMAT - Hazardous Material.

Hematogenous - Produced by or derived from the blood.

Hematuria - Blood in the urine.

Hemolysis - Separation of the hemoglobin from the red blood cells and its appearance in the plasma.

Hyperemia - An excess of blood in a part.

Hypertension - Persistently high arterial blood pressure.

Hypoplasia - Incomplete development or underdevelopment of an organ or tissue.

Hypotension - Abnormally low blood pressure.

Hypovolemia - Abnormally decreased volume of circulating fluid in the body.

Hypoxemia - Deficient oxygenation of the blood (hypoxia).

Hypoxia - Low oxygen content or tension.