A tetrahedron.
A triangular pyramid.
A tetrahedron.
a tetrahedron
A tetrahedron.
As answered on another link, it's a tetrahedron, provided the faces are equal
The name is derived from Greek roots, and so the name, not surprisingly, is "tetrahedron".
Tetrahedron. http://en.wikipedia.org/wiki/Tetrahedron
tetrahedron
A tetrahedron.
tetrahedron
Tetrahedron