The study of gases, clusters, liquids, and solids as units or systems, eventually focuses on the properties of these systems as governed by interactions between atoms, molecules, and radicals that are not covalently bonded to one another. The stereo/spatial properties of molecular species themselves are similarly controlled, with such interactions found throughout biological, polymeric, and cluster systems and are a central feature of chemical reactions. Nevertheless, these interactions are poorly described and characterized, with efforts to do so, usually based on a particular quantum or even classical mechanical procedure, obscuring the fundamental nature of the interactions in the process. Intra- and Intermolecular Interactions Between Noncovalently Bonded Species addresses this issue directly, defining the nature of the interactions and discussing how they should and should not be described. It reviews both theoretical developments and experimental procedures in order to explore interactions between nonbonded entities in such a fundamental manner as to elucidate their nature and origins. Drawing attention to the extensive experience of its editor and team of expert authors, Intra- and Intermolecular Interactions Between Noncovalently Bonded Species is an indispensable guide to the foundational knowledge, latest advances, most pressing challenges, and future directions for all those whose work is influenced by these interactions.• Comprehensively describes the nature of interactions between nonbonded species in biological systems, liquids, crystals, clusters, and in particular, water.• Combines fundamental, theoretical, background information based on various approximations with the knowledge of experimental techniques.• Outlines interactions clearly and consistently with a particular focus on frequency and time-resolved spectroscopies as applied to these interactions.