What is a Venn Diagram?

A Venn diagram is defined as a method to find out the similarities and differences between two or more groups, which are represented as circles. Variables that overlap are shared qualities between the groups. Variables that do not overlap are dissimilarities.

The method is named after John Venn (1834 – 1923), an English mathematician, who popularised the system in the 1880s.

Venn diagram explained

Reading a Venn diagram is relatively easy. It’s been used since the mid-20th century to introduce the basics of logic to elementary school children. A Venn diagram is used in mathematics, specifically in areas of logic theory and set theory, which deal with multiple sets of data and the relationship between groups.

Important terms in a Venn diagram

Let’s look at some of the terms used in a Venn diagram. 

1. Set: A set is a group or collection of items, products, members, etc.

2. Union: The constituents of a set.

3. Intersection: The items overlapping/being common across sets.These are also known as subsets.

4. Absolute complement: Everything that is not present in a set. 

5. Relative complement: Items present in one set but not in the other.

Types of Venn diagrams

There are different types of Venn diagrams: two-set; three-set; four-set; five-set; and multiset Euler diagrams, named after Swiss mathematician Leonard Euler (1707 - 1783).

Let’s take a look at two types of Venn diagrams.

A basic Venn diagram begins with a two-set diagram, which features two overlapping sets. If these two sets do not overlap, it’s known as a two-set Euler diagram. If one of the sets totally envelops the other set, the diagram is called both a Venn and a Euler. 

In a three-set Venn diagram, the part where all three circles overlap is called the union. If one of the sets does not overlap, it’s not a three-set diagram. One of the sets may be completely enveloped within any of the other two circles as well, making it the nested set.

Venn diagram example

Let’s consider the simplest two-set Venn diagram. 

Imagine that in a class of 50 pupils, there are two sets of students who like Snickers and Mars. Let’s call the first set of students ‘Set A’ and the second ‘Set B’. The union of Set A and Set B would comprise students who like both Snickers and Mars.