ABSTRACT
Nonlinear systems behave naturally. Our experience and experiments are proving that every day. However, our students are indoctrinated by the linear theories throughout their first years of study. We have to admit that we also contribute to that through our lectures. So, it seems appropriate, at the beginning of this book, to briefly present properties or dynamical phenomena of nonlinear systems in order to refresh our knowledge about some types of dynamic behavior which we all experience more or less in our surroundings or in the laboratory. Some basic definitions and theorems which will be useful for understanding the subsequent text are also given here. Definitions have to be mathematically rigorous and maybe for some of our readers not so appealing.
