
related topics 
{math, energy, light} 
{math, number, function} 
{line, north, south} 
{@card@, make, design} 
{household, population, female} 

In geometry, a 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 the only convex polyhedron that has four faces.^{[1]}
The tetrahedron is the threedimensional case of the more general concept of a Euclidean simplex.
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 a triangular pyramid.
Like all convex polyhedra, a tetrahedron can be folded from a single sheet of paper. It has two nets.^{[1]}
For any tetrahedron there exists a sphere (the circumsphere) such that the tetrahedron's vertices lie on the sphere's surface.
Contents
Full article ▸


related documents 
Curvature 
Polyhedron 
Map projection 
Gaussian beam 
Stereographic projection 
Electrical impedance 
Virial theorem 
Nucleon 
Geographic coordinate system 
Alcubierre drive 
Star cluster 
Electromagnetism 
Velocity 
Hall effect 
Superfluid 
Focal length 
Retrograde and direct motion 
BornOppenheimer approximation 
Comoving distance 
Vulcan (hypothetical planet) 
Albedo 
Čerenkov radiation 
Zodiac 
Phobos (moon) 
Boltzmann constant 
Voyager 2 
Red dwarf 
Kinetic theory 
Auger electron spectroscopy 
Ellipse 
