The subject of functional equations in one of the esoteric part of mathematics never taught in schools. Nevertheless, it makes its appearence in IMO, repeatedly. In fact, Olympiad competitions world over have generated innumerable problems in functional equations and put forth new ideas of solving them. This lead me to rewrite the book that was first brought out in 2002. The general structure of this book is based on the original work and the title remains the same. But I have included more chapters to look at the subject in micro level. I have also discussed more problems, many of them being of recent origin. Each problem itself is an island and method may be unique to itself. But there are some global threads which I have tried to bring out to understand the general principle of functional equations.

Each chapter contains substantial number of exercises. Besides, there is a collection of 101 problems at the end. Some of these exercises / problems are easy and some are hard. I have not classified them.