Etymology Dictionary

RADIUS,  a ray.  (L.)   In Phillips, ed. 1710.   Chiefly used in mathematics.—Lat. radius, a ray; see Ray.   Der. radi-al, from F. radial, 'of, or belonging to, the upper and bigger bone of the arme,' Cot., formed with suffix -alis from Lat. radius, sometimes used to mean the exterior bone of the fore-arm.   Also radi-ant, spelt radyaunt in Fisher, On the Seven Psalms, Ps. 130, ed. Mayor, p. 231, last line, from radiant-, stem of pres. part. of Lat. radiare, to radiate, from radius; and hence radi-ant-ly, radi-ance.   Also radi-ate, from Lat. radiatus, pp. of radiare.   Also radiat-ion, in Bacon, Nat. Hist. § 125, near the end, from F. radiation, 'a radiant brightness,' Cot., which from Lat. radiationem, acc. of radiatio, a shining, from pp. radiatus.