Venn Diagram

Also called a Venn diagram, it was invented in 1881 by British mathematician John Venn. It's a way of visually showing the mathematical or logical relationships between sets. Usually, a rectangle represents the overall space, while circles or ovals represent specific sets. Overlapping circles show common elements, and separate ones indicate no intersection. You can easily see unions, intersections, and so on, though you can't list the exact elements precisely. Initially, this method mainly dealt with relationships among four sets, but later it was expanded to handle more sets. Nowadays, it's widely used in computer file management, teaching, and clinical thinking analysis.