This book offers an essential introduction to fuzzy logic, starting with the classical notions and going through more advanced notions from the current state-of-the-art research. Each of the major topics is accompanied by examples, problems and Scilab codes. As a free open source software, Scilab offers everyone the chance to practice the concepts learned through the book. The book represents a synthesis of authors' research and experience through the lectures delivered to university students. It is primarily intended as a textbook for upper-level undergraduates and graduates in computer science, mathematics, physics and engineering. It also represents a valuable resource for practitioners and researchers alike, bringing ideas for projects in the broad field of fuzzy logic.