In ancient Rome what was a triclinium?

A 'triclinium' (plural: 'triclinia') is a formal dining room in a Roman building. The word is adopted from the Greek τρικλίνιον, triklinion, from τρι-, tri-, "three", and κλίνη, klinē, a sort of "couch" or rather chaise longue. Each couch was sized to accommodate a diner who reclined on their left side on cushions while some household slaves served multiple courses rushed out of the culina, or kitchen, and others entertained guests with music, song, or dance.

Smaller 'triclinia' would be used for smaller dinner parties, with a more exclusive set of guests. Hence their decoration was often at least as elaborate as that found in larger 'triclinia'. As in the larger 'triclinia', wine, food, and love were always popular themes. However, because of their association with patronage and because dining entertainment often included recitation of high-brow literature like epics, dining rooms could also feature more "serious" themes. As in many houses in Pompeii, here the smaller dining room ('triclinium minus') forms a suite with the adjoining 'cubiculum' and bath.