Lewis & Short

rădĭus, ii, m. [cf.: radix, ramus], a staff, rod.

  1. I. In gen.: acuti radii immissi, stakes, Liv. 33, 5, 11: ferreus, Plin. 10, 42, 58, § 117.
    1. B. In partic.
      1. 1. A spoke of a wheel, Plin. 16, 40, 76, § 206; Verg. G. 2, 444; id. A. 6, 616; Ov. M. 2, 108; 2, 317; Val. Fl. 6, 414: inter radios rotarum, Curt. 4, 9, 5; Plin. 16, 40, 76, § 206.
      2. 2. In mathematics,
        1. a. A staff, rod, for measuring, etc., Cic. Tusc. 5, 23, 64; Verg. E. 3, 41; id. A. 6, 850; Macr. S. 7, 2; Tert. Idol. 9.
        2. b. A semidiameter, radius of a circle, Cic. Univ. 6.
      3. 3. In weaving, a shuttle, Ov. M. 6, 56; 132; Lucr. 5, 1352; Verg. A. 9, 476.
      4. 4. In zoology,
        1. a. The spur of many kinds of birds, Plin. 11, 47, 107, § 257; esp. of the cock, id. 30, 11, 29, § 97.
        2. b. The sting above the tail of the fish pastinaca, Plin. 9, 48, 72, § 155; 32, 2, 12, § 25.
      5. 5. In botany, a kind of long olive, Verg. G. 2, 86; Col. 5, 8, 4; id. Arb. 17, 3; Plin. 15, 3, 4, § 13. A sub-species of the same, called radius major, Cato, R. R. 6, 1; Varr. R. R. 1, 24.
      6. 6. In anatomy, the radius, the exterior bone of the forearm, Gr. κερκίς, Cels. 8, 1.
      7. 7. Radius virilis = membrum virile, Cael. Aur. Acut. 3, 14, 115.
  2. II. A beam or ray of any shining object; of the sun, Plaut. Mil. 1, 1, 2; Lucr. 1, 48; 2, 117; Cic. Fin. 5, 24, 71; Verg. A. 4, 119; 7, 25; Tert. Res. Carn. 47; of lightning, Verg. A. 8, 429; Val. Fl. 6, 55; of the eyes, Gell. 5, 16, 2; of the halo around the heads of divine or deified personages: aurati, Verg. A. 12, 163; cf. radio, II.