in Geometry, the difference between two incommensurable lines.

in Music, the difference between a greater and a lesser semi-tone; expressed by the ratio, 128; 125.

APOTROPÆ, (from ἀποτρέπω, I avert), in the ancient poetry, verses composed for averting the wrath of incensed deities; and the deities invoked for averting any threatened misfortune were called Apotropæans; they were also called Alexiaci, from ἀλέξω, I drive away; and Averruncii from averruco, which denotes the same.