 It should be pointed out that no particular interpretation is intended in an abstract dynamical system. We have motivated the definition with an example from mechanics, but dynamical systems are not tied to that context. They are mathematical objects in their own right, and as such they can be studied independently of particular applications. This makes them a versatile tool in many different domains. In fact, dynamical systems are used, among others, in fields as diverse as physics, biology, geology and economics. 