http://www.ratinghq.comRatinghq Category Comments Feed for Physical sciencesRatingHQ (http://www.ratinghq.com)enA tetrahedron (plural: tetrahedra) is a polyhedron composed of four triangular faces, three of which meet at each vertex. A regular tetrahedron is one in which the four triangles are regular, or "equilateral", and is one of the Platonic solids. The tetrahedron is one kind of pyramid, which is a polyhedron with a flat polygon base and triangular faces connecting the base to a common point. In the case of a tetrahedron the base is a triangle (any of the four faces can be considered the base), so a tetrahedron is also known as triangular pyramid. Like all convex polyhedra, a tetrahedron can be folded from a single sheet of paper.http://www.ratinghq.com/5-895/tetrahedron.html2008-09-11 04:55:58