American Heritage® Dictionary of the English Language, Fourth
Edition - n. A diagram using circles to represent sets, with the
position and overlap of the circles indicating the relationships
between the sets. - n. set theory 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 , where n is the number of
depicted sets which are proper subsets of the universal set. -
n. a diagram that uses circles to represent mathematical or
logical sets pictorially inside a rectangle (the universal set);
elements that are common to mo