plagal

adjective Music.

1. (of a Gregorian mode) having the final in the middle of the compass.Compare authentic(def 6a).

adjective

1. (of a cadence) progressing from the subdominant to the tonic chord, as in the Amen of a hymn
2. (of a mode) commencing upon the dominant of an authentic mode, but sharing the same final as the authentic mode. Plagal modes are designated by the prefix Hypo- before the name of their authentic counterpartsthe Hypodorian mode

adj.1590s, from Medieval Latin plagalis, from plaga “the plagal mode,” probably from plagius, from Medieval Greek plagius “plagal,” in classical Greek “oblique,” from plagos “side” (see plagio-).