Feature geometry is a phonological theory which represents distinctive features as a structured hierarchy rather than a matrix. Feature geometry grew out of autosegmental phonology, which emphasizes the autonomous nature of distinctive features. However, feature geometry recognizes that subsets of features often pattern together and formally encodes the groups of features into nodes. Common nodes in feature geometries are Laryngeal and Place nodes. The Laryngeal node is an organizing node that dominates the features of the larynx, usually taken to be [voice], [constricted glottis], and [spread glottis]. The Place node is the dominant node of the place features. The Root node is the formal organizing unit of the segment, and in some frameworks encodes the major class features such as [consonantal], [sonorant], and [approximant]. Some features such as [nasal] and [lateral] are dependent from the root node. Other features such as [anterior] and [distributed] are usually dependent from the Coronal place feature.
The first formal model of feature geometry was introduced in print by George N. Clements in 1985, drawing on unpublished work by K.P. Mohanon and Joan Mascaró. Another precursor to feature geometry was proposed by Roger Lass in 1976, in which he proposed a laryngeal feature submatrix within a distinctive feature matrix. Other important models have been proposed by Elizabeth Sagey (1986), John J. McCarthy (1988), and Clements & Hume (1995). Models vary widely in the number of the hierarchical nodes and in how consonant and vowel features are treated.