A set is a collection of well-defined objects in the real or thought world. For example , a set of three textbooks on Bengali , English and Mathematics. The first ten sets of odd natural numbers, sets of integers, sets of real numbers, and so on. The set is usually represented by the capital letters A, B, C, ........... X, Y, Z of the English alphabet . For example , a set of numbers 3, 2, 4, 6 A = {2, 4, 6 প্রত্য Each object or member of the set is called the element of the set . For example , if B = a, b , the elements of set B are a and b; The expression symbol ' ∈ ' ∴ a ∈ B and is read , a, the member of B ( a belongs to B) b ∈ B is read b, the member of B ( b belongs to B) There is no c element in the upper B set . Method of describing sets The set is expressed in two ways. Namely: (1) list method and (2) set formation method.