Pyramid

A pyramid is a polyhedron that has a base, which can be any polygon, and three or more triangular faces that meet at a point called the apex. These triangular sides are sometimes called the lateral faces to distinguish them from the base.

The base

The base can be any polygon, but is most often a square.

The base is usually a regular polygon, but it need not be.

The faces

The faces of the pyramid are all triangles. If the base is a regular polygon, the triangles are all congruent (same shape and size), and isosceles (two sides the same length).

Right and Oblique pyramids

• If the apex is directly over the center of a regular base as it is above, it is called a right pyramid.
• If the apex is not over the center of the base, it is called an oblique pyramid, and the faces are not congruent.