A polyhedron is the three-dimensional version of a polygon: it is a chunk of space with flat walls. In other words, it is a three-dimensional figure made by gluing polygons together. The word is Greek in origin, meaning many-seated. The plural is polyhedra. The polygonal sides of a polyhedron are called its faces.
Collect some triangles, either the snap-together plastic polydrons or paper triangles. Try gluing them together in various ways to form polyhedra.
Table 1: The first 20 Greek number prefixes
A regular polygon is a polygon with all its edges equal and all angles equal. A regular polyhedron is one whose faces are regular polygons, all congruent, and having the same number of polygons at each vertex.
For homework, construct models of all possible regular polyhedra, by trying what happens when you fasten together regular polygons with 3, 4, 5, 6, 7, etc sides so the same number come together at each vertex.
Make a table listing the number of faces, vertices, and edges of each.
What should they be called?