ensible form, hopefully complete, intelligible, and unambiguous to the recipient. With this background in mind, we can conceive of information as taking different forms: a sensory input, an identification pattern, a game or process rule, a set of facts or instructions meant to guide choices or actions, a record for future reference, a message for immediate feedback. So information is diversified and conceptually intractable. Let us clarify here from the inception and quite frankly: a theory of information is unable to tell what information actually is or may represent in terms of objective value to any of its recipients! As we shall learn through this series of chapters, however, it is possible to measure information scientifically. The information measure does not concern value or usefulness of information, which remains the ultimate recipient's paradigm. Rather, information theory provides mathematical methods for informatio, in the ancestral Latin sense, but, since the twentieth century, using powerful computer technologies, which make it possible to handle phenomenal amounts of raw information messages. This chapter will help us to conceive the "measure of information" in the Shannon or "classical" definition, which represents the central axiom in information theory. We will do this in two steps. First, we will analyze in what ways information might "make sense," but without any philosophical pretence. It is important in our view to go through this preliminary reflection before approaching information theory. No doubt, it has the potential to open up many interesting discussions and stimulate a brainstorming session, which could eventually get everyone lost in the class. However, the benefit of the reflection is to acquire the right focus, and safely engage us on the information-theory journey, which is a more practical and useful goal than that of philosophically mastering the information concept. Measuring information Making sense of information In ordinary life and circumstances, information represents any