Apredella is the base on which an altarpiece sits. It is usually decorated with sculpture relief or painting and the subject chosen normally refers to that of the main scenes of the altarpiece. So, for example, the predella in Gentile da Fabriano's Adoration of the Magi (1423; Florence, Uffizi) complements the central scene with narratives from the infancy of Christ, namely the Nativity, Flight into Egypt, and Presentation in the Temple. Giovanni Bellini's Pesaro Altarpiece (1470s; Pesaro, Museo Civico) includes St. George along the frame and his killing the dragon on the predella. A final example is Fra Angelico's Linaiuoli Altarpiece (1433; Florence, Museo di San Marco), which shows Sts. Peter and Mark in the outer panels and St. Peter Preaching and the Martyrdom of St. Mark on the predella.
Historical dictionary of Renaissance art. Lilian H. Zirpolo. 2008.