Michael Halliday’s social semiotic theory is an important part of the theoretical background of O’Halloran’s contribution to this volume. In this introduction to O’Halloran’s chapter, Jensen, therefore, introduces the key ideas and concepts of Halliday’s theories, focusing especially on the concepts of ‘semiotic resource’, the idea of semiotic choice, and the relationship between language and reality, and how these concepts and ideas are important to O’Halloran’s text.