In a certain field of thinking object, thinking object can exist in two different ways. One is a collection of similar molecules, and the other is a class of objects with the same properties. The basic operations of a set are intersection, union, relative complement, absolute complement and subset.
(1) intersection: In set theory, let A and B be two sets, and the set composed of all elements belonging to set A and set B is called the intersection of set A and set B, and is recorded as AOB.
(2) Union: Given two sets A and B, the set consisting of all their elements is called the union of set A and set B, which is denoted as AUB and pronounced as A and B.