This book systematically presents and develops a scientific theory of gearing, specifically for those involved in gear design, analysis, and manufacture. The author begins with a few simple postulates that form the foundation of the theory of gearing. The postulated concepts are limited just to two entities, namely to (a) rotation vectors of the driving shaft and of the driven shaft, and to (b) torque on the driving shaft. The rest of the design parameters of an optimal gear pair are derived from the above mentioned input information-- Provided by publisher.