Three-Dimensional Shapes
Three-Dimensional Shapes
Definition Solid Geometry
In solid geometry, we study three-dimensional (3D) shapes, such as cubes, cylinders, and spheres. The diagrams below show some examples of these shapes.
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Definition Surface
A surface is the outside of a three-dimensional (3D) shape. It is the part of the shape you can touch.
Definition Face
A face is a flat surface on a three-dimensional shape.
Definition Edge
An edge is a straight line where two faces meet.
Definition Vertex
A vertex is a corner of a three-dimensional shape. It is a point where two or more edges meet.
Example
This box-shaped solid has many faces, edges, and vertices. One example of each is shown.
Classification
Definition Classification
We can sort three-dimensional (3D) shapes by counting their faces, edges, and vertices. Some examples are shown in the table below.
| Name | Shape | Faces | Edges | Vertices |
| Cube |  | 6 (flat faces) | 12 | 8 |
| Sphere | | 1 (curved surface) | 0 | 0 |
| Square Pyramid |  | 5 (flat faces) | 8 | 5 |
| Cylinder |  | 3 (1 curved, 2 flat faces) | 0 | 0 |