Regular tetrahedron

Regular tetrahedron
Type	Platonic solid
Faces	4 regular triangles
Edges	6
Vertices	4
Symmetry group	Tetrahedral symmetry $\mathrm {T} _{\mathrm {h} }$
Dihedral angle (degrees)	70.5°
Dual polyhedron	self-dual
Properties	convex, regular
Net

A regular tetrahedron is a tetrahedron composed of regular triangular faces, three meeting at each vertex. It is an example of Platonic solids, described as cosmic stellation by Plato in his dialogues. The regular tetrahedron, as well as the other Platonic solids, has been described by mathematicians and philosophers since antiquity.

All the faces of a regular tetrahedron are equilateral triangles of the same size, and exactly three triangles meet at each vertex. A regular tetrahedron is convex, meaning that for any two points within it, the line segment connecting them lies entirely within it.

It is one of the eight convex deltahedra because all of the faces are equilateral triangles. The regular tetrahedron is self-dual, meaning its dual is the regular tetrahedron itself. It has the tetrahedral symmetry $\mathrm {O} _{\mathrm {h} }$.. Its Schläfli symbol is {3,3}.