Segmental Features in Phonology
This discussion is drawn primarily from T. A. Hall, Segmental Features in Paul de Lacy (ed.). The Cambrdige Handbook of Phonology. 2007. Cambridge University Press.
 Segments and Features
Segments in phonology are conceptualized as consisting of bundles of features, or feature-value pairs. In Feature Geometry, the features show a hierarchical structure; for example root features like consonantal or sonorant dominate lower features like continuant and class nodes like place. The outline below illustrates the hierarchical feature structure given in Hall's figure 2.
 A Feature Tree
 Major Class Features
From SPE: "[Consonantal] sounds are produced with a radical obstruction in the midsagital reagion of the vocal tract; nonconsonantal sounds are produced without such an obstruction."
The feature consonantal distinguishes stops, fricatives, nasals and liquids (+consonantal) from glides, vowels and laryngeals (-consonantal).
From SPE: "Sonorants are sounds produced with a vocal tract cavity configuration in which spontaneous voicing is possible."
The feature sonorant distinguishes stops and fricatives (-sonorant) from nasals, liquids, glides, vowels, and laryngeals (+sonorant).
Sounds that are +approximant have a constriction in the vocal tract that allows frictionless release of air.
 Laryngeal Features
 Manner Features
The feature continuant distinguishes stops from fricatives. Halle and Clements: "Continuants are formed with a vocal tract configuration allowing the airstream to flow through the midsaggital region of the oral tract."
Nasal sounds are produced by lowering the velum and allowing the air to pass outward through the nose; oral sounds are produced with the velum raised to prevent the passage of air through the nose.
Sounds that are +nasal include nasal consonants and nasal vowels, including less-common pre-nasalized stops, nasal glides, nasal fricatives, and nasal trills.
The nasal feature is usually considered to be a direct daughter of the root. It is sometimes considered privative, sometimes binary.
Halle and Clements:
Lateral sounds ... are produced with the tongue placed in such a way as to prevent the airstream from flowing outward through the center of the mouth, while allowing it to pass over one or both sides of the tongue; central sounds do not involve such a constriction.
In feature geometry, the lateral feature has been argued by some to be a dependent of coronal, while others argue that it is a direct daughter of the root node.
From SPE: "strident sounds are marked acoustically by greater noisiness than their nonstrident counterparts."
The strident feature is used to distinguish interdental fricatives (-strident) from alveolar fricatives (+strident); palatoalveolar (+strident) from palatal (-strident); affricates (+strident) from stops (-strident).
In feature geometry, strident may be located in the root, or as a daughter of coronal.
 Place Features
The Place node is parent to three articulator privative nodes: Labial, Coronal, and Dorsal, covering sounds made with the lips, tongue front, and the tongue dorsum, respectively. The Pharyngeal feature is treated separately.
Coronal sounds are those articulated using the front part of the tongue (i.e. the tongue tip, blade, and the forward part of the body). This includes dental, alveolar, retroflex, palatoalveolar, alveopalatal and palatal places of articulation. Some authors consider coronal to apply to front vowels, while others use it for consonants only.
In feature geometry, Coronal is a privative node mother to the anterior and distributed features.
The feature anterior distinguishes coronal sounds produced in front of the alveolar ridge from those produced behind it.
[The feature +distributed describes a] constriction formed by the tongue front that extends for a considerable distance along the direction of airflow and [-distributed] to a constriction formed by the tongue front that extends only for a short distance along the direction of airflow.
Apical sounds are -distributed; laminal sounds are +distributed.
Some authors have argued to replace distributed with back, capturing the relationships observed between, for example, retroflex consonants and back vowels.
Dorsal sounds are those involving the body of the tongue; this includes all vowels, velars, and uvulars. In feature geometry, Dorsal is mother to the features back, high, and low.
The back feature is mainly used to account for the distinction between front and back vowels.
Sagey: +high indicates a "raised tongue body" while -high indicates a tongue body which is "distinctively not raised".
Sagey: +low indicates a "lowered tongue body" while -low indicates a tongue body which is "distinctively not lowered."
The Advanced Tongue Root feature ATR is used to capture the distinction between /i e o/ and /ɪ ɛ ɔ/.
Sagey (1986) features for vowels:
Sagey (1986) features for velar and uvular consonants:
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