A Venn diagram is an often used tool in mathematics and set theory, where it is used to illustrate the logical relations between different sets. The Venn diagram has two key parts: the circles and the areas. The circles are usually drawn as ovals or circles, but other shapes may be used. The area of a circle is proportional to the number of elements it represents. In this section, I will be using a Venn diagram to show how unions can be represented by intersection and union operations on sets.