ABSTRACT
This chapter introduces the basic notions of complex systems. Reviewing the classifications commonly adopted in literature, a new perspective over complex systems is proposed that allows to discuss the concepts of nonlinearity, uncertainty, and system dimension unveiling the role that the interplay between them has in the emergence of complex behaviors. In order to provide the necessary guidelines to study and classify complex systems, the chapter considers the qualitative scheme. It establishes a strict link between dynamical complex systems, mathematical models, and electronic circuits and devices. The element of universality between different domains is that complex systems encompass both nonlinearity and uncertainty which are always present in electronic devices. As a consequence, despite the fact that nonlinearity and uncertainty make difficult the definition of a general theory to study such systems, they allow us to obtain reliable electronic setups showing complex behavior.
