Definition of radius noun from the Oxford Advanced Learner's Dictionary

     

    radius

     noun
    noun
    BrE BrE//ˈreɪdiəs//
     
    ; NAmE NAmE//ˈreɪdiəs//
     
    (pl. radii
    BrE BrE//ˈreɪdiaɪ//
     
    ; NAmE NAmE//ˈreɪdiaɪ//
     
    )
    Skeleton and muscles, Mathematical terminology
     
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  1. 1 a straight line between the centre of a circle and any point on its outer edge; the length of this line compare diameter See related entries: Mathematical terminology
  2. 2a round area that covers the distance mentioned from a central point They deliver to within a 5-mile radius of the store. Doctors wish to examine everyone living within a 10-mile radius of the factory.
  3. 3 (anatomy) the shorter bone of the two bones in the lower part of the arm between the elbow and the wrist, on the same side as the thumb see also ulna See related entries: Skeleton and muscles
  4. Word Origin late 16th cent. (in sense (3)): from Latin, literally ‘staff, spoke, ray’.
See the Oxford Advanced American Dictionary entry: radius