Webster's English Dictionary

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radius

1. ra.di.us \'ra-d-e--*s\ \-e--.i-\ n or ra.dii also ra.di.us.es [L, ray, 
   radius] pl  1a: the anterior and thicker and shorter bone of the human 
   forearm or of th e corresponding part of the forelimb of vertebrates above 
   fishes 1b: the third and usu. largest vein of an insect's wing  2: a line 
   segment extending from the center of a circle or sphere to the cu rve or 
   surface 3a: the distance of a radius  3b: the circular area defined by a 
   stated radius  3c: a bounded or circumscribed area  4: a radial part  5: 
   the distance from a center line or point to an axis of rotation  6: an 
   imaginary radial plane dividing the body of a radially symmetrical an imal 
   into similar parts
2. radius vt : to cut (as a fillet) on an arc of a circle