Sets

The concept of set serves as a fundamental part of present day mathematics. Today this concept is being used in almost every branch of mathematics. Sets are used to define the concepts of relations and functions. The study of geometry, sequences, probability, etc. requires the knowledge of sets. The theory of sets was developed by German mathematician Georg Cantor (1845-1918). 

We shall say that a set is a well-defined collection of objects. We give below a few more examples of sets used particularly in mathematics, viz. N: the set of all natural numbers Z: the set of all integers Q: the set of all rational numbers R: the set of real numbers Z+: the set of positive integers Q+: the set of positive rational numbers, and R+: the set of positive real numbers.