Though thermodynamics is a tool used in all sciences and technologies, this book is especially designed to acquaint science students with the whole breadth of the subject covering both equilibrium and non-equilibrium regions. Equilibrium thermodynamics covered in the first-seven chapters caters to the needs of students up to the B.Sc./B.Sc. (Hons.) level. The next three chapters devoted to non-equilibrium thermodynamics and network thermodynamics fulfill the needs of the syllabi on these topics introduced in most universities at the postgraduate level. Chapters on ‘The Question of Ideality’ and ‘The Non-linear Region’ were the new additions to the second edition. In the third edition a new chapter on “Causality Principle in Non-equilibrium Thermodynamics” has been added. The readers may find the new chapter intellectually stimulating. The book is an accessible, straightforward discussion of basic topics, beginning with the laws of thermodynamics and focusing on derivations of basic relations. The text is suitably illustrated throughout with examples of various applications of interest to science students. It explains concepts systematically, teaches problem-solving meaningfully, and includes concept-elucidating questions that are intended to reinforce the student’s understanding of the material.