This book provides a comprehensive investigation of the origins, development, and stabilization of differential object marking (DOM) in Romanian. DOM, a means by which a grammar distinguishes between objects based on semantic features such as animacy or definiteness, has been a fruitful area of research in syntax, historical linguistics, and typology. In this volume, Virginia Hill and Alexandru Mardale demonstrate that Romanian DOM reflects a typological mix of Balkan and Romance patterns, and is in fact composed of three distinct mechanisms. Their analysis of these mechanisms reveals that DOM triggers in Romanian are located in the nominal domain, in contrast to languages such as Spanish, where they are located in the verbal domain. The cross-linguistic perspective adopted in the volume sheds light on existing typologies of DOM, particularly in relation to the variation observed in the merging location of the DOM particle and of the doubling pronominal clitic.