Even though we use language constantly, we don’t normally pay a great deal of attention to it. When we do, it’s usually because something has gone wrong, or because we’re passionate about the topic or speaker. While we will consider cases where things go wrong, in this book we focus more often on how language works, in common situations, in different ways, for different people. Before we do this, we need to think about what ‘language’ is. This is not an easy task. What counts as a language is a political, cultural and technical question. At the same time, while a group of people may share a language, they will each have their own individual way of using that language. To make matters even more complicated, individuals don’t consistently use language in the same way. The language we use when we talk to our friends is not the same as the language we use to write a letter of complaint. Language varies depending on the people using it, the task at hand, and the society in which it all takes place.