This book aims to teach. It is directed to students. It is not directed to researchers.

Research literature is typically written in the third person. That is appropriate. In this book I will often write in the first person – there, I just did! – and address you – yes, you, the reader – in the second person. When I employ ‘we’ it is not as a royal plural, but as you and me together, author and reader, engaged in the common pursuit of applying ourselves to terahertz physics. I hope you are comfortable with, or will become comfortable with, this use of personal pronouns.

This book is a text book. So it contains text. But not unrelieved text. To give pedagogical structure, the text is divided into parts, into chapters, into sections and into subsections. But there is more, to accommodate different learning styles. Perhaps you are a visual learner; there are diagrams for you. Perhaps you are a native speaker of the language of mathematics; equations succinctly express much of the material. Perhaps you learn by example; there are examples sprinkled throughout. Perhaps you learn by doing; there are exercises aplenty. If you like reading dictionaries or telephone directories, you might like the glossary.