CALIBRATION	Determination of variation from standard, or accuracy, of a measuring instrument to ascertain necessary corection factors. The check or correction of the accuracy of a measuring instrument to assure proper operational characteristics.
CATION	A positively charged ion.
CHAMBER, IONIZATION	An instrument designed to measure a quantity of ionizing radiation in terms of the charge of electricity associated with ions produced within a defined volume.
CHARGED PARTICLE	An ion. An elementary particle carrying a positive or negative electric charge.
CHRONIC EXPOSURE	The absorption of radiation or ingestion of a radionuclide during a lifetime.
COMMITTED DOSE EQUIVALENT	The dose equivalent to organs or tissues of reference that will be received from an intake of radioactive material by an individual during the 50 year period following the intake.
COMMITTED EFFECTIVE DOSE EQUIVALENT	The sum of the products of the weighting factors applicable to each of the body organs or tissues that are irradiated and the committed dose equivalent to these organs or tissues.
CONTAMINATION	Deposition of radioactive material in any place where it is not desired,  particularly where its presence may be harmful.
CONTROLLED AREA	A defined area in which the occupational exposure of personnel to radiation or radioactive material is under the supervision of the Radiation Safety Officer.
COSMIC RADIATION	Penetrating ionizing radiation, both particulate and electromagnetic, originating in space. Secondary cosmic rays, formed by interactions in the earth's atmosphere, account for about 45 to 50 millirem annually.
COULOMB	The meter-kilogram-second unit of electric charge equal to the quantity of charge transferred in one second by a constant current of one ampere.
COUNT	The external indication of a device designed to enumerate ionizing events. It may refer to a single detected event or to the total registered in a given period of time. The term is often erroneously used to designate a disintegration, ionizing event, or a voltage pulse.
COUNTER, GEIGER	A highly sensitive, gas-filled radiation measuring device.
COUNTER, PROPORTIONAL	A gas-filled radiation detection device whereby the pulse produced is proportional to the number of ions formed in the gas by the primary ionizing particle.
COUNTER	The combination of phosphor, photomultiplier tube and associated circuitry for counting light emissions produced in the phosphors.
CRITICAL ORGAN	The body organ receiving a radionuclide or radiation dose that results in the greatest overall damage to the body.
CURIE (Ci)	The quantity of any radioactive material in which the number of disintegrations is 3.7 E10 per second.