A winged altarpiece or winged retable is a special form of altarpiece, common in Northern and Central Europe, in which the central image, either a painting or relief sculpture can be hidden by hinged wings. It is called a triptych if there are two wings, a pentaptych if there are four, or a polyptych if there are four or more. The technical terms are derived from Ancient Greek: τρίς: trís or "triple"; πέντε: pénte or "five"; πολύς: polýs or "many"; and πτυχή: ptychē or "fold, layer".