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Polyhedrons are solid 3D shapes, made up from flat 2D Polygon faces, though as this page will show, there are different types of Polyhedrons.
Shapes such as a cuboid or a pyramid, are examples of common Polyhedrons.
The pyramid on the left is made up of 5 flat faces, which includes the square base, as well as the triangle faces.
The cuboid on the right, is made up of 6 flat faces, again including the base.
A regular Polyhedron is a 3D shape where all the faces are identical Polygons of exactly the same size, as such all the edges of a regular Polyhedron are of equal length.
There are however, only 5 such Polyhedrons, they are known as the Platonic Solids.
These polyhedrons are the only 5 3D shapes that consist of regular polygon faces that are all equal in size.
More information specifically on the Platonic Solids can be seen at the following web pages.
Prisms are a type of Polyhedron.
Prisms are 3D shapes that have 2 parallel faces(bases) at opposite ends, that are the same shape.
These bases are joined together by flat rectangle shaped faces between them.
Prisms are named accordingly to the shape of the bases.
Below are 3 common prisms.
In the Triangular Prism, there are 2 triangle shaped bases, joined by 3 flat faces between them.
In the Pentagonal Prism, there are 2 pentagonal shaped bases, joined by 5 flat faces between them.
If all sides on the bases of a prism are the same length, then it is classed as a regular prism.
If not, then it is an irregular prism.
The three prisms shown above, triangular, square and pentagonal, are regular prisms. As the parallel bases were regular polygons with all edges the same length.
A basic example of an irregular prism is a rectangular prism.
A right prism is a prism where the bases align with eachother, and are joined together by rectangle faces.
When the bases don't align with eachother, then the prism is an oblique prism, and the faces between the bases are parallelograms, as opposed to rectangles.