Definition of set: A set is a collection of well-defined objects. Explanation of the term “Well-defined”: Well-defined means, it must be absolutely clear that which object belongs to the set and which does not. Now, to get basic concepts of sets about the meaning of well-defined the following examples are given below. 1. The collection of vowels in English alphabets. This set contains five elements, namely, a, e, i, o, u. 2. A group of “Singers with ages between 18 years and 25 years” is a set, because the range of ages of the singer is given and so it can easily be decided that which singer is to be included and which is to be excluded. Hence, the objects are well-defined. 3. A collection of “Red flowers” is a set, because every red flowers will be included in this set i.e., the objects of the set are well-defined. . The collection of past presidents of the United States union is a set. 5. A group of “Young dancers” is not a set, as the range of the ages of young dancers is not g