Mathematics is a way of thought. Attaining a deep understanding of mathematics is more than mastering a collection of theorems, definitions, problems, and techniques; it is understanding how theorems and definitions fit together with the overall strategy of arguments presented. This introduction to real analysis contains thorough and complete proofs with lively and generous explanation to guide the reader through the foundations and the way of analysis. Real analysis, in one and several variables, is developed from the construction of the real number system to an introduction to the Lebesgue integral. Additionally, there are three chapters on applications of analysis, ordinary differential equations, Fourier series, and curves and surfaces, to show how the techniques of analysis are used in concrete settings.