👉 Tetralogies are a type of mathematical notation used in set theory, where two sets have exactly three elements. This means that each element in one set must be present in both sets to form a complete and distinct subset of the other set. For example, in set theory, if A = {1, 2, 3} and B = {4, 5}, then the set C = {1, 4, 5} is a tetralogy of sets
