What exactly is Product Modularity? The answer depends on who you ask

'Product modularity' has recently experienced a significant increase in interest in the academic literature. While the concept of product modularity is used across a wide range of academic research areas, substantial variations exist in the ways in which the concept is described and interpreted. In this paper, I develop a framework to represent the similarities and differences that appear across these variations of the concept of product modularity. Next, through an extensive literature search I construct a set of 85 references representing the use of product modularity in the engineering and management literature over the past 30 years (1975–2006). With help of the framework I then analyze the use and interpretation of product modularity in every reference in the set. The analysis demonstrates that the product modularity concepts taken together really encompass a bundle of product characteristics rather than a single condition, and individual research areas exhibit certain preferences in which they define and operationalize product modularity. I conclude with some recommendations for future research. Overall, this paper strives to provide a vocabulary to improve cross-disciplinary understanding of product modularity