Name & describe prisms & pyramids
Theory
A prism is named by the shape of its two matching ends; a pyramid is named by its base and narrows to an apex. Solids are described by their faces, edges and vertices.
A prism is a solid with two identical parallel ends joined by rectangles. It is named by the shape of its ends: a triangular prism has triangular ends, a rectangular prism has rectangular ends.
A pyramid has one base and triangular faces that rise to a single point called the apex. It is named by its base: a square pyramid has a square base.
Every solid can be described by its faces (flat surfaces), edges (lines where two faces meet) and vertices (corners).
Counting the parts helps describe and tell solids apart.
| Solid | Faces | Edges | Vertices |
|---|---|---|---|
| Rectangular prism | 6 | 12 | 8 |
| Triangular prism | 5 | 9 | 6 |
| Square pyramid | 5 | 8 | 5 |
How to name and describe a solid
- Look for matching ends. Two identical parallel ends means it is a prism, named by those ends.
- Look for an apex. Triangular faces meeting at a point means it is a pyramid, named by its base.
- Count the faces, edges and vertices to describe it fully.
The ends are triangles, so it is a triangular prism.
The faces come in opposite pairs.
| \(2 + 2 + 2\) | \(=\) | \(6\) |
There are three rings of four edges.
| \(4 + 4 + 4\) | \(=\) | \(12\) |
The base is a square, so it is a square pyramid.
Common pitfalls
Frequently asked questions
How is a prism named?
A prism is named by the shape of its two matching ends, called its cross-section. Triangular ends make a triangular prism; rectangular ends make a rectangular prism.
What is the difference between a prism and a pyramid?
A prism has two identical parallel ends joined by rectangles. A pyramid has one base and triangular faces that meet at a single point called the apex.
What are faces, edges and vertices?
A face is a flat surface, an edge is a line where two faces meet, and a vertex is a corner where edges meet.
How many faces does a rectangular prism have?
Six. They come in three opposite pairs: two ends, top and bottom, and front and back.
How is a pyramid named?
A pyramid is named by the shape of its base. A square base makes a square pyramid; a triangular base makes a triangular pyramid.