radio-

CIDE DICTIONARY

radio-, a. 

•  Of or pertaining to, or employing, or operated by, radiant energy, specifically that of electromagnetic waves with frequencies between those of infrared radiation and X-rays; hence, pertaining to, or employed in, broadcast radio or television, microwaves, radiotelephones, etc.; as, radio waves.  [Webster 1913 Suppl.]
•  of or pertaining to broadcast radio; as, a radio program.  [PJC]

radio-,  

 A combining form indicating connection with, or relation to, a radius or ray; specifically (Anat.), with the radius of the forearm; as, radio-ulnar, radio-muscular, radio-carpal.  [1913 Webster]

OXFORD DICTIONARY

radio-, comb. form 1 denoting radio or broadcasting.
2 a connected with radioactivity. b denoting artificially prepared radioisotopes of elements (radio-caesium).
3 connected with rays or radiation.
4 Anat. belonging to the radius in conjunction with some other part (radio-carpal).

Etymology

RADIUS + -O- or f. RADIO