2. Prisms and pyramids have what's called a base. The base is the face with the property that if you cut the solid anywhere parallel to the surface of the base, the same shape will appear at the cut.

Example:

Identify the base of the following polyhedra. Why is this the base?

a.)
(b.)

Solution:

a.) The base is the square. This is because the square is the only face with the property that if you cut the pyramid anywhere parallel to the surface of the square, the same shape will appear at the cut (even though it may be smaller).

b.) The base is the pentagon. Again, this is the only face with the property that cutting the solid anywhere parallel to it will produce a cut of the same shape.

The relationship between the name of the object and what it looks like is that the first word of the name gives the shape of the base, and the second word gives the type of solid it is. For example, for a pentagonal prism the base would be a pentagon and the solid would be a prism.