In most grammatical models, hierarchical structuring and dependencies are considered as central features of grammatical structures, an idea which is usually captured by the notion of “head” or “headedness”. While in most models, this notion is more or less taken for granted, there is still much disagreement as to the precise properties of grammatical heads and the theoretical implications that arise of these properties. Moreover, there are quite a few linguistic structures that pose considerable challenges to the notion of “headedness”.Linking to the seminal discussions led in Zwicky (1985) and Corbett, Fraser, & Mc-Glashan (1993), this volume intends to look more closely upon phenomena that are considered problematic for an analysis in...