# Venn diagram

Venn diagram illustrating two sets, S_{1} = {*a*, *b*, *c*, *d*, *e*} and
S_{2} = {*b*, *d*, *f*, *g*} for
which the intersection of S_{1} and S_{2}, S_{1} ∩ S_{2} = {*b*, *d*} and their union, S_{1} ∪ S_{2} = {*a*, *b*, *c*, *d*, *e*, *f*, *g*}.

A Venn diagram is a simple way of representing sets and subsets,
which makes use of overlapping circles. Venn diagrams are named after the
Englishman John Venn (1834–1923), a fellow of Cambridge University.
Venn was a cleric in the Anglican Church, an authority on what was then
called "moral science," the compiler of a massive index of all Cambridge
alumni, and a rather mundane mathematician who worked in logic and probability
theory. The diagrams he used for representing syllogisms appear to have been first called "Venn diagrams" by Clarence Irving in his
book *A Survey of Symbolic Logic* in 1918. However, Venn was lucky
to be so immortalized. Both Gottfried Leibniz and Leonhard Euler used very similar forms
of representation many years earlier.