Venn diagram is constructed with a collection of simple closed curves drawn in the plane. 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 comprise overlappin, the "principle of these diagrams is that classes be represented by regions in such relation to one another that all the possible logical relations of these classes can be indicated in rcles. The interior of the circle symbolically represents the elements of the set, while the exterior represents elements which are not members of the set. For instance, in a two-set Venn diagram, one circle may represent the group of all wooden objects, while another circle may represent the set of all tables. The overlapping area or intersection would then represent the set of all wooden tables. Shapes other than circles can be employed, and this is necessary for more than three sets. Venn diagrams do not generally contain information on the relative or absolute sizes