The Greek ordinal adjective dōdekatos (δωδέκατος) means 'twelfth' and is derived from dōdeka (twelve). In the New Testament it appears in Revelation 21:20 describing the twelfth foundation of the New Jerusalem, adorned with amethyst.
The number twelve is foundational to God's covenant structure: twelve tribes of Israel, twelve apostles, twelve foundations and twelve gates of the New Jerusalem (Revelation 21). The twelfth foundation, made of amethyst, is part of the complete picture of divine beauty and permanence. The New Jerusalem's twelve-fold structure signals the perfect completion of both Old and New Covenant communities — the twelve tribes and twelve apostles together form the eternal city's foundation (Revelation 21:14). Every 'twelfth' detail points to God's absolute faithfulness to complete what He began.