[i]Wavefront Analysis[/i] is Part III of a series of books on [i]Optical Imaging and Aberrations[/i]. It has evolved out of the author's work and lectures over the years on wavefront analysis as applied to optical design and testing. Its focus is on the use of orthonormal polynomials that represent balanced classical aberrations in optical imaging systems with pupils of various shapes. After a brief introduction to optical imaging, aberrations, and orthonormalization of a set of polynomials over a certain domain to obtain polynomials that are orthonormal over another domain, this book describes in detail the polynomials appropriate for various shapes of the system pupil. Starting with the system that is most common in imaging, namely, the one with a circular pupil, systems with annular, hexagonal, elliptical, rectangular, square, and slit pupils are considered. Included in this list are also systems with circular and annular pupils with Gaussian illumination, anamorphic systems with square and circular pupils, and those with circular and annular sector pupils. These chapters start with a brief discussion of aberration-free imaging that includes both the PSF and the OTF of a system. A separate chapter is devoted to a discussion of the pitfalls of using the Zernike circle polynomials for systems with noncircular pupils by applying them to systems with annular and hexagonal pupils. Similarly, a chapter is devoted to the calculation of orthonormal aberration coefficients from the wavefront or the wavefront slope data. Each chapter ends with a brief summary that describes the essence of its content.