Lewis & Short

dī-mĭdĭus, a, um, adj. [medius], half (for the diff. between it and dimidiatus, v. dimidio).

  1. I. As an adj., until the Aug. per. only in connection with pars, e. g.: dimidiam partem nationum subegit, Plaut. Curc. 3, 77; id. Aul. 4, 10, 37; id. Rud. 4, 4, 79; Lucr. 1, 618 sq.; 5, 720; Cic. N. D. 2, 40, 103; id. Rosc. Com. 11, 32; id. Fam. 13, 29, 4; Caes. B. G. 6, 31, 5; id. B. C. 1, 27; 3, 101 (twice); Sall. J. 64, 5; Suet. Caes. 42; Front. Strat. 2, 3, 21; Ov. F. 5, 122; id. Tr. 1, 2, 44 et saep.
  2. II. Since the Aug. per., esp. in poets, also with other substantives, instead of dimidiatus (v. dimidio), divided into two equal parts, halved: mullus (opp. lupus totus), Mart. 2, 37, 4: crus, Juv. 13, 95: vultus, id. 15, 57: Memnone, id. 15, 5: forma circuli, Plin. 2, 59, 60, § 150: clepsydrae, id. Ep. 6, 2, 5: labro basia dare, i. e. slightly, Mart. 2, 10 and 22; so of busts: Priapus, Mart. 11, 18; cf. Cicero’s pun on the half-length likeness of his brother Quintus: frater meus dimidius major est quam totus, in Macr. S. 2, 3 (the word dimidius, for dimidiatus, belongs prob. to Macr. himself).
  3. III. Trop., so of persons of mixed descent: dimidius patrum, dimidius plebis, half patrician and half plebeian, Liv. 4, 2, 6.
    Hence, subst.
    1. A. dīmidium, ii, n., the half (very freq. in all periods and kinds of writing): horae, Lucil. ap. Gell. 3, 14, 11; so with gen., Plaut. Am. 5, 1, 73; id. Bacch. 5, 2, 67; 71 et saep.; absol., Plaut. Bacch. 2, 3, 87; id. Ps. 4, 7, 68; 5, 2, 29; id. Pers. 1, 2, 17 et saep.; abl. dimidio, with comparatives: dimidio minus opinor, less by half, Plaut. As. 2, 4, 35; Cic. Att. 9, 9, 2; id. Fl. 20, 46; id. Verr. 2, 3, 33; Caes. B. G. 5, 13, 2; Hor. S. 2, 3, 318 et saep.
      1. 2. Like a comp. with quam: vix dimidium militum quam quod acceperat successori tradidit, Liv. 35, 1, 2; 45, 18, 7.
        Prov.: dimidium facti, qui coepit, habet, well begun is half done, Hor. Ep. 1, 2, 40; cf. Aus. Ep. 81.
    2. B. Rarely dī-midia, ae, f. (sc. pars), the half: verbenaca decocta in aqua ad dimidias, Plin. 26, 12, 73, § 120.