Despite a rich academic literature in the field of intellectual property (IP), there has been little conceptual analysis of the subject matter that IP rights protect, and in reflection of this, little attention paid to the meaning of the terms used to denote those subject matter, including ‘invention’, ‘authorial work’, ‘trade mark’, and ‘design’. This book offers such an analysis, the first of its kind, with the aim of furthering understanding of each IP regime and of IP in general. By means of a nominal word:thing definitional exercise, it studies the terms in question with reference to their recent use by IP legal officials in order to offer a conceptual understanding of the objects that they denote. The analysis proceeds in three main stages. At the first stage, the context in which the relevant terms fall to be defined is considered, with a particular focus on the nature, aims, and values of IP rights and systems. At the second stage, a theoretical framework for thinking about the subject matter protectable by IP in general is proposed, and certain focal questions for understanding such subject matter are derived. And finally, at the third stage, officials’ use of the legislative terms that denote the subject matter protectable by IP regimes are considered in detail and the results of that consideration used to answer the focal questions. The result is a definition of each of the terms with reference to the objects that they denote, with a particular focus on the categories and properties of the subject matter protectable by each IP regime, the methods by which those subject matter are individuated within each regime, the relationship between each subject matter and its concrete instances, and the manner in which each subject matter and its instances is known.