1, 2, 3, 4, . . ., natural numbers. 0, zero. -1, -2, -3, -4, . . ., negative integers. Rational numbers, irrational numbers, real numbers, complex numbers, . . ., and, what are numbers? The most accurate mathematical answer to the question is given in this book. The book is intended to be a supplement to textbooks on the differential and integral calculus. Those who are studying the subject should read this book. However, prerequisites are kept...