hēmĭtŏnĭum, ĭi, n., = ἡμιτόνιον,
a half-tone , semitone : intervalla tonorum et hemitoniorum, Vitr. 5, 4, 3; Mart. Cap. 9, § 930; 963; Hyg. Astr. 4, 14; Macr. S. 2, 1, 22.