A pictorial representation of propositions (1) or sets (1) by means of overlapping circles (see illustration). A Venn diagram is a refined and improved version of it. Also called Euler's circles. [Named after the Swiss mathematician Leonhard Euler (1707–83) who introduced them and used them extensively]
Euler diagram. The four basic relations between two sets, A and B. The first diagram at the top shows ‘some A are not B’. The two diagrams below it show ‘some A are B’ and ‘all B are A’ The bottom diagram shows ‘no A is B’.