The work of 65 eminent scientists from 13 countries, this book introduces various aspects of density functional theory (DFT) and their connections to chemical reactivity theory. The text examines bonding, interactions, reactivity, dynamics, toxicity, and aromaticity as well as fundamental aspects of DFT. Several chapters provide a review of the key global and local reactivity descriptors and their variations under different perturbations. While this volume is designed for readers with little or no prior knowledge of the subject, the breadth of the book and the expertise of the authors ensure that even experienced scientists will benefit from the information in these pages.