The paper presents an in-depth study of focus marking in Gùrùntùm, a West Chadic language spoken in Bauchi Province of Northern Nigeria. Focus in Gùrùntùm is marked morphologically by means of a focus marker a, which typically precedes the focus constituent. Even though the morphological focus-marking system of Gùrùntùm allows for a lot of fine-grained distinctions in information structure (IS) in principle, the language is not entirely free of focus ambiguities that arise as the result of conflicting IS- and syntactic requirements that govern the placement of focus markers. We show that morphological focus marking with a applies across different types of focus, such as newinformation, contrastive, selective and corrective focus, and that a does not have a second function as a perfectivity marker, as is assumed in the literature. In contrast, we show at the end of the paper that a can also function as a foregrounding device at the level of discourse structure.

Three dimensions can be distinguished in a cross-linguistic account of information structure. First, there is the definition of the focus constituent, the part of the linguistic expression which is subject to some focus meaning. Second and third, there are the focus meanings and the array of structural devices that encode them. In a given language, the expression of focus is facilitated as well as constrained by the grammar within which the focus devices operate. The prevalence of focus ambiguity, the structural inability to make focus distinctions, will thus vary across languages, and within a language, across focus meanings.