An octahedron is a closed 3-d shape with 8 polygonal faces. There are 257 topologically different convex octahedra. They can have faces which are triangles, quadrilaterals, pentagons, hexagons or heptagons.
The answer to your question, is an Octahedron.
It can be but need not be. A heptagon-based pyramid is an octahedron. However, the term is often used for the Platonic solid bounded by eight equilateral triangles - in the form of two square based pyramids stuck together base-to-base.
A regular tetrahedron. octahedron, dodecahedron.
A regular octahedron is a Platonic solid with equilateral triangles for each of the faces. A heptagonal pyramid is an octahedron with one heptagon (a seven sided figure) as its base and 7 triangles, one attached to each side, meeting at the either vertex.
This object is called an octahedron
An octahedron is a closed 3-d shape with 8 polygonal faces. There are 257 topologically different convex octahedra. The various octahedra have faces which may be triangles, quadrilaterals, pentagons, hexagons or heptagons. Any one of these could be a base.
An octahedron is a closed 3-d shape with 8 polygonal faces. There are 257 topologically different convex octahedra. They can have faces/bases which are triangles, quadrilaterals, pentagons, hexagons or heptagons.
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.
It can be a heptagon (heptagonal pyramid), hexagon (hexagonal prism), square (square based bipyramid). There are versions with pentagonal or triangular bases but I cannot think of their names.
A tetrahedron, a triangle based pyramid, an octahedron, an icosahedron plus many more.
One difference: An octahedron has 8 faces, a triangular prism has 5. An octahedron (="eight faces") is a regular high-symmetry solid with all the faces identical. A triangular prism has a triangular base, a triangular roof, and 3 rectangular sides (walls).
hexagonal prism In geometry, the hexagonal prism is a prism with hexagonal base. This polyhedron has 8 faces, 18 edges, and 12 vertices. Since it has 8 faces, it is an octahedron. However, the term octahedron is primarily used to refer to the regular octahedron, which has eight triangular faces. https://en.wikipedia.org/wiki/Hexagonal_prism#/media/File:Hexagonal_prism.png