A triptych is a series of three separate paintings that together form a story. The word comes from the Greek adjective triptukhon (three-fold), from tri, (three) and ptysso, (to fold) or ptyx, (fold) The paintings are usually joined together, with hinges, so that they can be folded shut or displayed open. The middle painting is usually larger, although they can be of equal size.
A triptych is usually an art work, but the word can be used for anything in three parts which join together to make a single item. 
The English painter William Etty painted a 28 ft (8.5 m) wide and 9 ft 9 in (3 m) high triptych of the life of Saint Joan of Arc. Etty sold the painting to an team of an engraver and dealer who went bankrupt in 1852. The paintings were separated and sold by 1893. The first panel which showed Joan of Arc finding the sword in the church of St. Catherine de Fierbois ended up in the collection of Llantarnam Abbey, Cwmbran, South Wales, U.K.. The Second panel is in the collection of the Musée des Beaux-Arts d'Orléans. The third panel has since been lost.
- "triptych". Online Etymology Dictionary.
- "Triptych". Merriam-Webster Dictionary. Retrieved January 28, 2017.
Although triptych originally described a specific type of Roman writing tablet that had three hinged sections, it is not surprising that the idea was generalized first to a type of painting, and then to anything composed of three parts.
- [Description of first panel from British Museum website catalog:"Title: Joan of Arc, On finding in the church of St Catherine de Frébus the sword she dreamt of, devotes herself & it to the service of God & her country. Description: Joan of Arc kneeling in a church, next to a tomb under a trefoil arch inscribed 'Valiant et Contstant' with a helmet beside it, holding a sword in her right hand, raising her left arm to heaven; after Etty. 1851" at .A study by Eddy for the "Joan of Arc" painting can be found online at Artworks Website U.K.]
- James Hamilton's "A Strange Business: Art, Culture, and Commerce in Nineteenth Century London" 2015
- A [copyrighted picture of the left handed panal can be found on page 317 of William Etty: The Life and Art By Leonard Robinson 2007]
- Another version of a C.W. Wass engraving can be found on the Library of Congress website