Feature Geometry

Feature geometry organizes distinctive features into a hierarchical tree of nodes, so that phonological processes can refer to functionally related groups of features as units.

Definition

A model of distinctive features in which features are organized hierarchically under class nodes, allowing processes to target functionally coherent groups of features.

Scope

This topic covers the development of distinctive feature theory in which features are not an unstructured set but are arranged in a hierarchy, with features grouped under class nodes such as a place node or laryngeal node, which themselves attach to the root node of a segment. This structure explains why certain features pattern together in assimilation and other processes—for instance, why place features spread as a group. It treats the motivation for the hierarchy and its relation to autosegmental representation. The treatment is descriptive and analytic.

Core questions

• Why organize distinctive features into a hierarchy?
• What class nodes group features together?
• How does the geometry explain that some features spread as a unit?
• How does feature geometry relate to autosegmental representation?

Key theories

Hierarchical organization of features

Clements's proposal that features are arranged in a geometry of nodes beneath a root node, so that class nodes such as the place node dominate related features and can be manipulated as single units in spreading and delinking.

History

Feature geometry arose in the mid-1980s, notably in Clements's 1985 paper, as a refinement of the flat feature set of The Sound Pattern of English. It drew on autosegmental representation and was developed further with proposals about articulator-based organization in subsequent work.

Debates

The correct structure of the feature tree

Proposals differ on how many class nodes there are and how features are grouped—for example, whether organization should be articulator-based—since competing geometries predict different sets of possible natural classes and processes.

Key figures

• George N. Clements
• John Goldsmith
• Bruce Hayes

Seminal works

• clements1985
• goldsmith1995

Frequently asked questions

What is a class node in feature geometry?

A class node is a node in the feature tree that groups together a set of related distinctive features, such as a place node dominating the features for labial, coronal, and dorsal articulation, so that they can be referred to as a unit.

What does feature geometry explain that a flat feature set does not?

It explains why certain features consistently pattern together in phonological processes; for example, when place of articulation spreads in assimilation, all the relevant place features move together because they are dominated by a single place node.