A trilithon or trilith[1] is a structure consisting of two large vertical stones (posts) supporting a third stone set horizontally across the top (lintel). It is commonly used in the context of megalithic monuments. The most famous trilithons are those of Stonehenge in England.
The word trilithon is derived from Greek 'having three stones' (τρι- tri- 'three' + λίθος líthos 'stone') and was first used in its modern archaeological sense by William Stukeley.
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