This Encyclopaedic Dictionary of Science is an effort to keep pace w ith continuing rapid developments and expanding vocabularies in various branches of science. This dictionary has been encyclopaedic in its contents and style of representation. Throughout the process of compilation and editing the volumes, the main effort was to make the dictionary serve as a ready reference for undergraduate and postgraduate students of science and for those appearing for competitive examinations, research scholars, teachers and authors. The entries have been written in a clear and explanatory style to provide both straight forward definitions and invaluable background information. This approach, combined with an extensive cross reference system, enables the reader to place the each entry into a broader scientific context. At certain appropriate places, the diagrams have been included whenever the meaning of a word can be best understood by means of a diagram. The presentation throughout has been aimed at sustaining the interest of readers while enriching their vocabulary and comprehension of technical terms and expressions of various branches of science. This encyclopaedic dictionary will be of immense value to the students of science and to scientists and research scholars working on science projects.