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radiometer
radiometric dating
radiomimetic
radionics
radionuclide
radiopaque
radiopharmaceutical
radiophone
radiophotograph
radioprotective
radioresistant
radioscopy
radiosensitive
radiosonde
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radius

ra·di·us [ ráydee əss ] (plural ra·di·i [ ráydee  ] or ra·di·us·es)


noun 
Definition:
 
1. mathematics line from center: a straight line extending from the center of a circle to its edge or from the center of a sphere to its surface.
Symbol  r


2. mathematics length of radius: the length of a radius.
Symbol  r


3. circular area: an area enclosed by a circle that has a radius of a particular length
all the houses within a radius of 2 miles of the explosion

4. range of effectiveness or influence: the area or range within which somebody or something can act, work, or exert influence effectively
beyond the radius of the governor's influence

5. anatomy bone in arm or forelimb: the shorter and thicker of the two bones in the human forearm, the one on the thumb side, or the equivalent bone in the lower forelimbs of animals

6. radiating part: a radiating line, part, or structure

[Late 16th century. < Latin, "staff, spoke, ray, beam of light"]
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