An octahedron is a closed 3-d shape with 8 polygonal faces. There are 257 topologically different convex octahedra. The simplest octahedron to make is probably the heptagon based right pyramid. The net for this shape is a regular heptagon with seven identical triangles attached to its edges. If the triangles are folded to meet at a point above the heptagonal base you will have an octahedron.
An octahedron is a 3D shape with 8 sides.
Octahedron
Octahedron
octahedron
An octahedron
An octahedron.An octahedron.An octahedron.An octahedron.
Octahedron
a octahedron
It is an octahedron that is a 3D shape with 8 faces
The suffix "hedron" implies 3D. The 2D suffix is "gon"
octagon-2D Octahedron-3D
An octahedron