Theoretical approaches to grammatical tone

Tone is distinct from other phonological phenomena both qualitatively and quantitatively (Hyman 2011), and has been instrumental in shaping phonological theory in many ways. However, the contributions to current linguistic theory of “grammatical tone’ (GT) – a type of non-concatenative morphology where a morpheme is expressed at least in part by tone and/or tone changes – have been less apparent. In this paper, we take stock of the types of GT patterns attested in the literature and the different theoretical treatments of GT that have been proposed to date. We show that GT is still to a large extent underexplored, and highlight the immense potential of the study of GT for improving our understanding of phonology and its outer limits. This paper serves as an introduction to the high-quality research articles collected in this special issue, which directly address how GT critically informs phonological theory and its current developments.