• 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 counterparts
• 3. Compare authentic
• 4. C16: from Medieval Latin plag a lis, from plaga, perhaps from Greek plagos side

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