Absorbed Dose - The energy imparted by ionizing radiation per unit mass of irradiated material. The units of absorbed dose are the RAD and the gray (Gy).

Alpha Particle - A type of particle that can be emitted during a radioactive decay.

Alpha Probe - A probe used to measure the presence of alpha particles.

Anorexia - Lack or loss of the appetite for food.

Antibody - A protein synthesized by an animal in response to the presence of a foreign substance or an immunoglobulin molecule synthesized on exposure to antigen, which can combine specifically with that antigen.

Antigen - A substance that can induce an immune response. Proteins, polysaccharides, and nucleic acids are effective antigens.

Anuria - Absence of excretion of urine from the body.

Aphonia - Loss or speech resulting from disease or injury to the speech organs.

Areflexia - Absence of reflexes.

Arthralgia - Pain in a joint.

Asthenia - Lack or loss of strength and energy.

Ataxia - Inability to coordinate muscular movements.

Autonomic - Self-controlling.

Bacteremia - The presence of bacteria in the blood.

Bacteria - Free-living organisms consisting of nuclear material, cytoplasm, and a cell membrane that divide by simple division.

Beta Particle - An electron emitted from a nucleus during a radioactive decay. Beta radiation is a skin hazard in addition to being an internal hazard.

Biological Agent - A microorganism (or toxin derived from it) which causes disease in man, plants or animals or which causes deterioration of material.

Biological Weapon - An item of material that projects, disperses, or disseminates a biological agent; including arthropod vectors.