Relations

A relation is simply a connection between two sets of things. For instance, if you have a set of students and a set of subjects, the idea "is enrolled in" pairs each student with the subjects they study. In mathematics, we make this precise by defining a relation as a subset of the Cartesian product $A \times B$, meaning it is a collection of ordered pairs $(a, b)$ where $a$ is related to $b$. This formal definition lets us study patterns like "i …