A well-defined collection of objects is known as a set. This concept, in its complete generality, is of great importance in mathematics since all of mathematics can be developed by starting from it. The various pieces of furniture in a given room form a set. So do the books in a given library, or the integers between 1 and 1,000,000, or all the ideas that mankind has had, or the human beings alive between one billion . and ten billion . These examples are all examples of finite sets, that is, sets having a finite number of elements. All the sets discussed in this book will be finite.
