 As a final preliminary to our more detailed history and analysis, we note that there is important variation between authors in whether “sortal” is applied to linguistic items, e.g., words like “cat” or “lake” or “cloud”; abstract entities such as the property of being a cat or of being a lake or a cloud; or to psychological entities such as the idea or concept of a cat or lake or cloud. The first interpretation views sortals as being linguistically determined.The second sees sortal categories as part of the world’s furniture independent of how we describe it, and the last is associated with a range of positions in between. These three different interpretations of the nature of sortals have been labeled as nominalist, realist, and conceptualist, respectively. Work on sortals may, in general, be classified under one of these three categories.