A trilithon (or trilith)'s a structure consisting of two large vertical stones (posts) supporting a third stone set horizontally across the top (lintel). Commonly used in the context of megalithic monuments. The most famous trilithons are those of Stonehenge in England and those found in the Megalithic temples of Malta, which are a UNESCO World Heritage Site. The word trilithon's derived from the Greek 'having three stones' (Tri - three, lithos - stone) and was first used by William Stukeley. Th… (More on Trilithon)