What changes in conceptual change?

This paper has two aims. First, it reviews literature about conceptual change and about the study of concepts more broadly. The principal claim is that much prior work has suffered from inexplicitness and imprecision in terms of what constitutes a concept. Second, we introduce a theory of one particular type of concept. A coordination class is a systematic collection of strategies for reading a certain type of information out from the world. We identify both structural components and performance properties of coordination classes. Using this theory, we analyse protocol data from a student with respect to the difficult concept of force in Newtonian mechanics.