The stibadium (plural: stibadia) is a later form of the Roman lectus triclinaris, the reclining seat used by diners in the triclinium. Originally, the lecti were arranged in a group of three in a semi-circle. The stibadium was a single semi-circular couch, fitting up to a dozen people, which replaced the triple group of lecti in the dining-room, frequently in alcoves around the centre of the room.
This ancient Roman furniture is also called sigma. This name comes from the lunate sigma (upper case C, lower case ϲ) — which resembles, but which is not at all related to, the Latin letter C and was used in Eastern forms of Greek writing and in the Middle Ages.
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