What are numbers? What are numerals? Are they the same? How precise are they? In this book, we will be focusing very closely at numbers and their properties and not numerals. We will basically consider two different kinds of numbers: precise numbers and imprecise numbers. The difference between these two kinds of numbers lies in their degree of precision. In case of a precise number, there is no room for error, whereas in case of an imprecise number, there can be some room for error as long as its value is reasonably close to the stated value. In Part I of this book, we will focus on precise numbers and number systems.Whereas Part II of this book is devoted for working with imprecise numbers. The first approach involves simplifying them by a mean and standard deviation. The second approach that we will explore involves determining the imprecise number's acceptable maximum and minimum end point values. Once we have found these values, we will discuss techniques for calculating the resultants after applying different functions and operations.Error Analysis is covered in Part III, where we discuss a new way to use our imprecise numbers. This approach lends itself to an easy implementation of a calculator or computer to calculate the error analysis.