Differential argument marking: Patterns of variation

In this introductory article we provide an overview of the range of the phenomena that can be referred to as differential argument marking (DAM). We begin with an overview of the existing terminology and give a broad definition of the DAM to cover the phenomena discussed in the present volume and in the literature under this heading. We then consider various types of the phenomenon which have figured prominently in studies of DAM in various traditions. First, we differentiate between arguments of the same predicate form and arguments of different predicate forms. Within the first type we discuss DAM systems triggered by inherent lexical argument properties and the ones triggered by non-inherent, discourse-based argument properties, as well as some minor types. It is this first type that traditionally constitutes the core of the phenomenon and falls under our narrow definition of DAM. The second type of DAM is conditioned by the larger syntactic environment, such as clause properties (e.g. main vs. embedded) or properties of the predicate (e.g. its TAM characteristics). Then, we also discuss the restrictions that may constrain the occurrence of DAM cross-linguistically, other typical features of DAM systems pertaining to the morphological realization (symmetric vs. asymmetric) or to the degree of optionality of DAM. Finally, we provide a brief overview over functional explanations of DAM.