In geometry|lang=en terms the difference between octahedron and tetrahedron
is that
octahedron is (geometry) a polyhedron with eight faces; the regular octahedron has regular triangles as faces and is one of the platonic solids while
tetrahedron is (geometry) a polyhedron with four faces; the regular tetrahedron, the faces of which are equal equilateral triangles, is one of the platonic solids.
As nouns the difference between octahedron and tetrahedron
is that
octahedron is (geometry) a polyhedron with eight faces; the regular octahedron has regular triangles as faces and is one of the platonic solids while
tetrahedron is (geometry) a polyhedron with four faces; the regular tetrahedron, the faces of which are equal equilateral triangles, is one of the platonic solids.