In this module we give an overview to the model of a system that will form the foundations for our discussion on nonlinear systems, we will quickly present the basic concepts from systems theory such as elements, system’s boundary, environment etc. There are many definitions for systems, we will just quickly present a few of them for you to get an idea of where they overlap. Your Dictionary defines a system as: An arrangement of things, or a group of related things that work toward a common goal. Webopedia tells us a system is: A group of interdependent items that interact regularly to perform a task. We will then loosely define a system as a set of parts that are interconnected in effecting some joint come.