ἡμι-τόνιον · hēmi-tonion — LSJ
semitone
semitone, Philol. 6, Aristox. Harm. p.21 M., al., D.H. Comp. 11, Arr. Epict. 2.11.2, etc.
II half the skein, bundle of gut
half the skein or bundle of gut in a torsion-engine, Ph. Bel. 68.46, Hero Aut. 2.6.
2 one of the two frames containing the τόνος
one of the two frames containing the τόνος in such an engine, Id. Bel. 90.4.