Aspects of the Theory of Definition.- I / Preliminary Considerations.- Real and Nominal Definitions.- Primitive Concepts: Habits, Conventions, and Laws.- II / Definitional Desiderata.- Vagueness and the Desiderata for Definition.- Definition in a Quinean World.- III / Formal Developments.- Definitions and Definability.- Towards a General Theory of Identifiability.- IV / Epistemic Dimensions.- Epistemic Terms and the Aims of Epistemology.- Rational Definitions and Defining Rationality.- V / Specialized Conceptions.- Idealized Definitions in Physics and Idealized Dispositions.- Inverted Definitions and Their Uses.- VI / Disciplinary Conceptions.- Definitions in Law.- Defining the Divine.- Philosophical Analyses: An Explanation and Defense.- Index of Names.- Index of Subjects.