Noah Webster
Apotome
APOT'OME,
APOT'OMY, noun [Gr. to cut off.]
1. In mathematics, the difference between two incommensurable quantities.
2. In music, that portion of a tone major which remains after deducting from it an interval, less by a comma, than a semitone major.
The difference between a greater and lesser semitone, expressed by the ratio 128; 125. The Greeks supposing the greater tone could not be divided into two equal parts, called the difference, or smaller part, apotome; the other, limma.