A diagram that uses circles to represent mathematical or logical sets pictorially inside a rectangle (the universal set); elements that are common to more than one set are represented by intersections of the circles WordNet 3.0 & Open English WordNet

A Venn diagram is a widely used diagram style that shows the logical relation between sets, popularized by John Venn in the 1880s. Wikipedia

A diagram type originally also called Euler circle Wikipedia Disambiguation

Diagram that shows all possible logical relations between a collection of sets Wikidata

A diagram representing some sets by contours of closed shapes, such as circles or ellipses (and sometimes also the universal set as a rectangle enclosing all of these shapes), and indicating the relationships between the sets: by overlapping the shapes to show that the corresponding sets have a non-empty intersection, and by possibly (but not necessarily) enclosing all of the sets (which are proper subsets of the universal set) within a universal set (represented typically by a rectangle); such that the total number of simply connected regions is 2 n , where n is the number of depicted sets which are proper subsets of the universal set. Wiktionary

Diagram representing sets by circles. Wiktionary (translation)