Definition:Tetrahedron

Definition

 * Tetrahedron.png

A tetrahedron is a polyhedron which has $4$ (triangular) faces.

Thus a tetrahedron is a $3$-simplex.

Also known as
A tetrahedron is also known as a '''triangular pyramid.

In, a tetrahedron is referred to as a pyramid (with / which has) a triangular base.

The first reference to it is in :