ABSTRACT
The concept of sets is basic to all mathematics and mathematical applications. Note, however, that the word “collection” is as undefined, in this setting, as is the word “set.” The diagrams are very simple and start by drawing a rectangle whose interior points represent the elements of the universal set. Any subset of the universal set is represented by a circle within the rectangle. The elements of the set are represented by the points inside the circle. The notions of union and intersection of two sets can be generalized to unions and intersections of more than two sets after introducing the notion of indexed family of sets.
