<human>:  What is the difference between a tetrahedron and an octahedron?
<bot>: The main difference between a tetrahedron and an octahedron is the number of faces each shape has. A tetrahedron has four faces, while an octahedron has eight faces. Another difference is that a tetrahedron has four triangular faces, while an octahedron has eight triangular faces. Finally, while a tetrahedron has four vertices, an octahedron has six.