Diptychs (Gr.Diptychs 060063 fromDiptychs 060064 twice, andDiptychs 060065 to fold), tablets anciently used for civil and ecclesiastical purposes. Among the Romans and Greeks, the term at the commencement of the Christian era designated two tablets united by a hinge, and used as a note book. Even when several tablets or leaves were included between the ornamented covers, they were still called diptychs. The tablets were made of ivory, wood, or metal, and sometimes of slate or papyrus, or of gold and silver. The external faces were more or less ornamented ; the interiors were smooth, so as to receive a coating of wax, or to admit leaves of parchment or papyrus. They were carried suspended to the belt or wrist; served for epistolary correspondence (in which case they were sealed by the writer before being sent to their destination); were presented as gifts by consuls and other high dignitaries to the emperors and senators, and to their friends and relatives; and were even distributed by them among the people on the occasion of the public games, etc.

The oldest consular diptychs known bear the date of A. D. 405, and are attributed to Stilicho. - In liturgical usage the diptychs were public lists or tables, which in the early church were read by the deacon from the ambon during the celebration of the liturgy. They contained, in so many separate columns or leaves, the names of the persons who made "the offering" that day ; those of the chief personages, lay and ecclesiastical, in communion with that particular church; the names of the saints, martyrs, and confessors of the faith ; and those of the faithful who had departed this life in the orthodox communion. Hence, to have the name of any person, living or dead, erased from the diptychs, was equivalent to an act of excommunication. - In art the name diptych is given to two panels united by a hinge, whose interior surface is painted. It is common to meet with such diptychs containing on one side the angel Gabriel, and on the other the Virgin Mary receiving his salutation. When there is a large central compartment, with two side panels folding over it, it is called a triptych.

Such is the celebrated Dombild or altarpiece of the cathedral of Cologne, having in the centre the adoration of the Magi, and on the sides the legend of St. Ursula and her companions.