One-third of a triptych is referred to as a PANEL. A triptych is a work of art that is divided into three sections, usually hinged together and often used as an altarpiece in churches. The term 'triptych' comes from the Greek adjective τρίπτυχον meaning 'three-fold'. Each PANEL of a triptych typically has its own subject, but all three panels are intended to be viewed together as a single work of art.