A Venn diagram is a diagram used to picture sets and the relationships between them. Circles and their interiors usually represent the sets, but almost any shape can be used.

Overlapping areas represent the intersection of the sets. Elements that belong to more than one set are placed where the circles overlap.

Areas of sets taken together represent the union of the sets.

Often the shapes are drawn inside a boundary representing a universal set. The size of the circles (or shapes) do not imply that one set is larger, smaller or the same size as another set.