This book presents a theory of phonological structures with roots in the framework of Dependency Phonology (henceforth DP), but proposes a rather different ‘geometry’, which reduces the set of unary elements to just two: |C| and |V| (which explains the name of the theory). The structure that is proposed accommodates all and only phonological distinctions that have been found to function contrastively in (at least one of) the world's languages. As such, the theory explains the set of contrastive distinctions, rather than (as is common) presenting it as a ‘random’ list (with or without a ‘random’ geometrical organisation). The book also provides an account of the relationship between syllable structure and segmental structure, but not in detail of phonological alternations (allomorphy). Although the theory mainly deals with spoken language phonology, it is also shown how it provides an account of segmental and syllabic structure in sign languages.

The proposal made here concurs with the view that the building blocks of segmental structures are unary elements, a view shared with models such as DP and Government Phonology (henceforth GP) as well as several other models. In agreement with DP and the approach called ‘Feature Geometry’ (henceforth FG), my proposal organises the elements into a segment-internal structure. Both this structure and the ‘syntax’ of element combinations are fundamentally based on the notion of dependency, with a striking recurrence of an ‘X-bar’-like structure (that is, a head with two levels of dependents). My proposal can be regarded as a metatheory of phonological features. It will be shown that many prior proposals for feature systems (for manner, place or laryngeal distinctions) find a ‘home’ in this model. The detailed analysis of phonological contrast provides a typological window on segmental and syllabic inventories in the world's languages, as well as on the relationship between these two levels.

The book introduces the reader to the central role of dependency relations in phonological structure, while advocating the idea that this structure can be derived from a small set of basic principles. Through comparison to other models, this work also provides a window on current theories of segmental structure, commonly used feature systems and recurrent controversies.