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A Venn diagram
is a visual tool used in describing how two or more sets are logically related to one another. The simplest example is a Venn diagram for two sets. Each set is represented by a planar region bounded by a circle, so that the two regions overlap. In the diagram below, set A is represented by the reddish circular disc and set B is represented by the bluish circular disc:
AA∩BB..
Typically, the two sets are subsets of some bigger set U, called a universe. Therefore, the corresponding Venn diagram above is shown to be sitting inside a larger rectangular region representing the universe:
2134U..
Notice that the region representing the universe U is partitioned into 4 mutually exclusive regions: