One of the mysteries of the English language finally explained.
A solid having four plane triangular faces; a triangular pyramid.
- ‘With his geodesic dome, Fuller began to express a favorite geometric shape of his, the tetrahedron, and he put it everywhere he could.’
- ‘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.’
- ‘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.’
- ‘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.’
- ‘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.’
- ‘These five remarkable solids - tetrahedron, cube, octahedron, dodecahedron, icosahedron - have faces that are congruent equilateral polygons.’
- ‘The strongest and most stable molecular structure is the three-dimensional tetrahedron, the configuration achieved with silicates.’
- ‘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.’
- ‘The new structure consists of 20 small crystalline tetrahedrons - pyramids with four triangular sides - that fit together a bit like sections of an orange.’
- ‘Quartz crystals are silicon atoms surrounded by a tetrahedron of oxygen atoms linked at shared corners.’
- ‘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 robot is called ‘TETwalker’ for tetrahedral walker, because it resembles a tetrahedron.’
- ‘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.’
- ‘He examined a vectorial system of geometry, Energetic - Synergetic geometry, based on the tetrahedron which provides maximum strength with minimum structure.’
- ‘Plato believed that atoms have the shapes of regular polyhedra: cubes, tetrahedrons, octahedrons, and so on.’
- ‘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.’
- ‘When all four corners of the tetrahedra are shared, the mineral is called a tectosilicate.’
- ‘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.’
Late 16th century: from late Greek tetraedron, neuter (used as a noun) of tetraedros ‘four-sided’.
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