 The study of inheritance systems attempts to synthesize recent discoveries about inheritance mechanisms and processes in nature with reflection about the nature and dynamics of evolutionary processes. The term “inheritance system” is typically used to refer to both mechanisms and factors involved in inheritance, but the term lacks a standard definition which goes beyond enumerating various purported inheritance systems, and it is unclear if a single definition can capture the different uses of the term. A principled definition that determines how inheritance systems are individuated and delimited—if indeed they can be— may be essential for addressing many conceptual issues that remain open (see Griesemer et al. 2005). The lack of a universally accepted definition may explain the fruitfulness of the term but also suggests approaching the literature with caution.