In a non-technical sense, a complex system is one in which the number of interacting independent components is large, there are multiple pathways by which the system can evolve over time, and whose evolution is sensitive to small perturbations or to initial conditions. In such systems, emergence of novel properties can occur (i.e., features that cannot be predicted from the system’s current specifications). More formally, it refers to an open system of many parts that have non-linear couplings among them. As such, the system can be discrete, and thus comply with set of difference equations as in cellular automata, or continuous as defined by a set of differential equations.
See Chaos, Complexity, Developmental emergence, Dynamical systems approaches, Emergence, Model, Model systems, Non-linear dynamical systems, Non-linear dynamics, Open system, Order, Organization, Self-organization, System