Parity time Symmetry and Its Applications Linear and Nonlinear Experiments in PT Symmetric Photonic Mesh Lattices PT Symmetry on a Chip: Harnessing Optical Loss for Novel Integrated Photonic Functionality Parity Time Symmetry in Scattering Problems Scattering Theory and PT Symmetry Passive PT symmetry in laser written optical waveguide structures Non Hermitian effects due to asymmetric backscattering of light in whispering gallery microcavities Exact Results for a Special PT symmetric Optical Potential Parity time symmetric optical lattices in atomic configurations Effects of exceptional points in PT symmetric waveguides Higher order exceptional points in discrete photonics platforms Non Hermitian Optical Waveguide Couplers Parity Time Symmetric Plasmonics PT symmetry and non Hermitian wave transport in microwaves and RF circuits Coupled nonlinear Schrodinger equations with gain and loss: modeling PT symmetry Making the PT symmetry unbreakable Krein signature in Hamiltonian and PT symmetric systems Integrable nonlocal PT symmetric and reverse space time nonlinear Schrodinger equations Construction of non PT symmetric complex potentials with all real spectra Constant Intensity Waves in Non Hermitian Media Nonlinear Beam Propagation in a Class of Complex Non PT Symmetric Potentials This book offers a comprehensive review of the state of the art theoretical and experimental advances in linear and nonlinear parity time symmetric systems in various physical disciplines and surveys the emerging applications of parity time (PT) symmetry. PT symmetry originates from quantum mechanics where if the Schrodinger operator satisfies the PT symmetry then its spectrum can be all real. This concept was later introduced into optics Bose Einstein condensates metamaterials electric circuits acoustics mechanical systems and many other fields where a judicious balancing of gain and loss constitutes a PT symmetric system. Even though these systems are dissipative they exhibit many signature properties of conservative systems which make them mathematically and physically intriguing. Important PT symmetry applications have also emerged. This book describes the latest advances of PT symmetry in a wide range of physical areas with contributions from the leading experts. It is intended for researchers and graduate students to enter this research frontier or use it as a reference book