The aim of compiling the `Dictionary of Science` is to provide descriptions of various terms of various branches of science from which the science students can extract the specific information. This dictionary includes most of the commonly used terms, statements, laws and techniques. This dictionary is a veritable mine of information. An elaborate system of cross- referencing marks the dictionary easy to use and extremely informative. At few places, diagrams have been used to illustrate the meaning of a term. Entries are compact but self-explanatory. SI units and IUPAC system of nomenclature have been used throughout this dictionary. Students, researchers, academics and teachers will find this dictionary most useful and informative. The present dictionary will also prove to be an invaluable reference guide for the informed lamer, with a professional interest in the subject. This dictionary will be useful and handy addition to your library to help you locate, identify and expound day-to-day terminology in its proper context.