The idea for this book originated with the late Igor Vasil 'evich Kurchatov. He suggested to the author the need for a comprehensive presentation of the fundamental ideas of plasma physics with­ out c'omplicated mathematics. This task has not been an easy one. In order to clarify the physical nature of plasma phenomena with­ out recourse to intricate mathematical expressions it is neces­ sary to think problems through very carefully. Thus, the book did not come into being by inspiration, but required a considerable effort. The aim of the book is to provide a beginning reader with an elementary knowledge of plasma physics. The book is primar­ ily written for engineers and technicians; however, we have also tried to make it intelligible to the reader whose knowledge ofphysics is at the advanced-freshman level. To understand the book it is also necessary to have a working knowledge of electricity and magnetism of the kind available in present-:day programs in junior colleges. This book is not intended for light reading. It is designed for the reader for whom plasma physics will be a continuing interest. We have confidence that such a reader will want to broad­ en his knowledge by consulting more specialized literature. Thus, we not only include simple expressions but also special important terms.