Venn Diagram

Diagrams that show all hypothetically possible logical relations between a finite collection of sets. Venn diagrams were invented around 1880 by John Venn. A Venn diagram is constructed with a collection of simple closed curves drawn in the plane. The principle of these diagrams is that classes or sets be represented by regions in such relation to one another that all the possible logical relations of these classes can be indicated in the same diagram. That is, the diagram initially leaves room for any possible relation of the classes, and the actual or given relation, can then be specified by indicating that some particular region is null or is not null. Venn diagrams normally consist of overlapping circles.