RADII is a playable word

radius Scrabble® Dictionary

noun
pl. radiuses or radii
a straight line from the center of a circle to the circumference
verb
radiused, radiusing, radiuses
to give a rounded form to
15 Playable Words can be made from "RADII"
   2-Letter Words (5 found)
   3-Letter Words (6 found)
   4-Letter Words (3 found)
   5-Letter Words (1 found)