Apotome

[Gr. apotemeo, to cut off.] ( Mus.) The difference between the greater and the le er semitone, being expre ed by the ratio of 128 to 125. (Geom.) The difference between two incommensurable lines or quantities. Thus the difference between the side of a square and its diagonal is the apotome, and is represented numerically by the expre ion 2-1. Brande .