An octahedron is the regular solid you are referring to. Octa- is the prefix for 8 sides.
Sounds like an octahedron.
There is no "regular pyramid". There are triangle pyramids, square pyramids, pentagon pyramids, etc. With the information given in your question, there is no way to answer.
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Geometric relationsThe cube is unique among the Platonic solids for being able to tile Euclidean space regularly. It is also unique among the Platonic solids in having faces with an even number of sides and, consequently, it is the only member of that group that is a zonohedron (every face has point symmetry).The cube can be cut into 6 identical square pyramids. If these square pyramids are then attached to the faces of a second cube, a rhombic dodecahedronis obtained.
It look like two square based pyramids stuck together on their square sides.
There are various types of pyramids, including regular pyramids (with a regular polygon as the base and congruent isosceles triangles as the faces), right pyramids (with the apex directly above the center of the base), and oblique pyramids (where the apex is not directly above the center of the base). Pyramids can also be classified based on the shape of their base, such as square pyramids, triangular pyramids, pentagonal pyramids, etc.
A regular pyramid is a right pyramid whose base is a regular polygon. There are only three regular pyramids: a regular tetrahedron, a regular square pyramid, and a regular pentagonal pyramid.
There are no regular solids with an odd number of sides and therefore no regular solids with 5 faces. For this reason there is no give name, as such, for a 5 faced solid. There are however non-regular solids which have 5 faces, such as a square pyramid and a triangle cylinder.
A raw diamond looks like two square pyramids attached at the base.
A regular octahedron - two square based pyramids stuck together along their square bases.
Well, honey, regular solids are like the popular kids of geometry - they have all their sides and angles looking symmetrical and sharp. Think of classics like cubes, pyramids, and good ol' prisms. These bad boys have faces that are all the same shape and size, making them the heartthrobs of the 3D shape world.
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