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A solid having four plane triangular faces; a triangular pyramid.
‘As water's temperature decreases to and falls below the normal freezing point, more and more of its molecules self-organize into clusters that have structures based on the tetrahedron, a pyramid with a triangular base.’
‘The new structure consists of 20 small crystalline tetrahedrons - pyramids with four triangular sides - that fit together a bit like sections of an orange.’
‘The tetrahedrite crystal on this specimen is a simple tetrahedron with very smooth, clean crystal faces and a bright, shiny metallic gray color (personal observation).’
‘The Enterprise Day at Joseph Rowntree School also involved representatives from The Institute Of Civil Engineers who built a giant tetrahedron with their young charges.’
‘He assigned the tetrahedron to fire, because the tetrahedron is the regular solid with the sharpest angles, and because fire is the most penetrating of elements.’
‘When all four corners of the tetrahedra are shared, the mineral is called a tectosilicate.’
‘Quartz crystals are silicon atoms surrounded by a tetrahedron of oxygen atoms linked at shared corners.’
‘The strongest and most stable molecular structure is the three-dimensional tetrahedron, the configuration achieved with silicates.’
‘These five remarkable solids - tetrahedron, cube, octahedron, dodecahedron, icosahedron - have faces that are congruent equilateral polygons.’
‘An artist can look at a mathematical shape and envision unlimited possibilities, even from a shape as seemingly simple as a tetrahedron, a trefoil knot, a Möbius strip, or a fractal surface.’
‘Plato believed that atoms have the shapes of regular polyhedra: cubes, tetrahedrons, octahedrons, and so on.’
‘For example, the convex hull of a 3D molecule is a convex polytope rather than a polygon, and it is tessellated by tetrahedra rather than triangles.’
‘The silica tetrahedra may also form a sheet structure where three oxygen atoms of each tetrahedron are shared by adjacent tetrahedra.’
‘With his geodesic dome, Fuller began to express a favorite geometric shape of his, the tetrahedron, and he put it everywhere he could.’
‘The robot is called ‘TETwalker’ for tetrahedral walker, because it resembles a tetrahedron.’
‘He examined a vectorial system of geometry, Energetic - Synergetic geometry, based on the tetrahedron which provides maximum strength with minimum structure.’
‘In particular he identified the five elements, fire, earth, air, water and celestial matter with the five regular solids, the tetrahedron, cube, octahedron, icosahedron and the dodecahedron.’
‘In the methane molecule CH 4, for instance, the carbon atom is located at the center of a tetrahedron with the four hydrogen atoms located at the four apexes of the tetrahedron.’
‘Whereas the tetrahedron is composed of four triangles, the pyramid, which looks a lot like it, is composed of four triangles and a square - the base.’
‘The four C-H bonds are directed towards the four corners of a tetrahedron, with carbon at its center and hydrogens at each vertex.’
Origin
Late 16th century: from late Greek tetraedron, neuter (used as a noun) of tetraedros ‘four-sided’.