- In geometry, a tetrahedron (pl.: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertices. The tetrahedron is the simplest of all the ordinary convex polyhedra.
- Armenia - The World Factbook (cia.gov)
Armenia prides itself on being the first state to formally adopt Christianity (early 4th century). Armenia has existed as a political entity for centuries, but for much of its history it was under the sway of various empires, including the Roman, Byzantine, Arab, Persian, Ottoman, and Russian.
