Introduction:-

In linguistics, a distinctive feature is the
most basic unit of phonological structure that may be analysed in phonological theory.

Distinctive features are grouped into categories according to the natural classes of segments they describe: major class features, laryngeal features, manner features, and place features. These feature categories in turn are further specified on the basis of the phonetic properties of the segments in question.

Since the inception of the phonological analysis of distinctive features in the 1950s, features traditionally have been specified by binary values to signify whether a segment is described by the feature; a positive value, [+], denotes the presence of a feature, while a negative value, [−], indicates its absence. In addition, a phoneme may be unmarked  with respect to a feature. It is also possible for certain phonemes to have different features across languages. For example, could be classified as a continuant or not in a given language depending on how it patterns with other consonants.

In recent developments to the theory of distinctive features, phonologists have proposed the existence of single-valued features. These features, called univalent or privative features, can only describe the classes of segments that are said to possess those features, and not the classes that are without them.

The central concern in this module is the nature of distinctive features. It will be concerned here with giving reasons for the need to have distinctive feature in phonological theory, the goals of a theory of distinctive features in phonology, a brief history of the development of the theory and the distinctive features. For lack of space, we take up a group of distinctive features – dorsal features- for discussion in the following module along with the question of how the distinctive features are used in the realization of the goals of the theory.

The theory of distinctive features has had a continuous history from the time of Trubebtzkoy (1939) and Jakobson (1968), leading figures of the Prague Linguistic Circle, in the period preceding the Second World War. It has undergone various revisions, the most noteworthy being Jacobson 1932, Trubetzkoy 1939, Jakobson, Fant and Halle, 1952, Jakobson and Halle 1956,

Chomsky and Halle, 1968, Clements, 1985, McCarthy, 1988. Of these, the conception of distinctive features and arguments for them presented in Chomsky and Halle (1968) are the basis of the features discussed here. The features themselves are as presented in the more recent works, e.g. Clements (1985) and McCarthy (1988). The difference between Chomsky and Halle (1968) and Clements (1985) and McCarthy (1988) is that the number of features is smaller in the latter, about 18, as compared to about 29 in the former.


  Major class features:- 

The features that represent the major classes of sounds.


1.[+/− syllabic] Syllabic segments may function as the nucleus of a syllable, while their counterparts, the [−syll] segments, may not. Except in the case of syllabic consonants, [+syllabic] designates all vowels, while [−syllabic] designates all consonants (including glides).


2.[+/− consonantal] Consonantal segments are produced with an audible constriction in the vocal tract, such as obstruents, nasals, liquids, and trills. Vowels, glides and laryngeal segments are not consonantal.


3.[+/− approximant] Approximant segments include vowels, glides, and liquids while excluding nasals and obstruents.


4.[+/− sonorant] This feature describes the type of oral constriction that can occur in the vocal tract. [+son] designates the vowels and sonorant consonants (namely glides, liquids, and nasals), that are produced without an imbalance of air pressure in the vocal tract that might cause turbulence. [−son] describes the obstruents, articulated with a noticeable turbulence caused by an imbalance of air pressure in the vocal tract.


Laryngeal Features:-

 : The features that specify the glottal states of sounds.

1.[+/− voice] This feature indicates whether vibration of the vocal folds occurs with the articulation of the segment.


2.[+/− spread glottis] Used to indicate the aspiration of a segment, this feature denotes the openness of the glottis. For [+sg], the vocal folds are spread apart widely enough for frication to occur; for [−sg], there is not the same friction-inducing spreading.


3.[+/− constricted glottis] The constricted glottis features denotes the degree of closure of the glottis. [+cg] implies that the vocal folds are held closely together, enough so that air cannot pass through momentarily, while [−cg] implies the opposite.


Manner Features:-

: The features that specify the manner of articulation.


1.[+/− continuant] This feature describes the passage of air through the vocal tract. [+cont] segments are produced without any significant obstruction in the tract, allowing air to pass through in a continuous stream. [−cont] segments, on the other hand, have such an obstruction, and so occlude the air flow at some point of articulation.


2.[+/− nasal] This feature describes the position of the velum. [+nas] segments are produced by lowering the velum so that air can pass through the nasal tract. [−nas] segments conversely are produced with a raised velum, blocking the passage of air to the nasal tract and shunting it to the oral tract.


3.[+/− strident] The strident feature applies to obstruents only and refers to a type of friction that is noisier than usual. This is caused by high energy white noise.


4.[+/− lateral] This feature designates the shape and positioning of the tongue with respect to the oral tract. [+lat] segments are produced as the center of the tongue rises to contact the roof of the mouth, thereby blocking air from flowing centrally through the oral tract and instead forcing more lateral flow along the lowered side(s) of the tongue.


5.[+/− delayed release This feature distinguishes stops from affricates. Affricates are designated [+del rel].


Place Features:-

The features that specify the place of articulation.


[ LABIAL ] Labial segments are articulated with the lips. As consonants, these include bilabial and labiodental consonants.


1.[+/− round]: [+round] are produced with lip rounding, while [−round] are not.


[ CORONAL ] Coronal sounds are articulated with the tip and/or blade of the tongue. These include a large number of consonants, which can be made with the tip, blade or underside of the tongue (apical, laminal, or subapical consonant, respectively), making contact with the upper lip (linguolabial), between the teeth (interdental), with the back of the teeth (dental), with the alveolar ridge (alveolar), behind the alveolar ridge (postalveolar), or on or in front of the hard palate ((pre)palatal). With postalveolar sibilants, additional tongue shapes need to be distinguished, i.e. "domed" or slightly palatalized ("hushing" or "palato-alveolar"), palatalized (alveolopalatal), and "closed" ("hissing-hushing").


[ DORSAL ] Dorsal sounds are articulated by raising the dorsum of the tongue. All vowels are dorsal sounds. Dorsal consonants include palatal, velar and uvular consonants.


[ RADICAL ] Radical sounds are articulated with the root of the tongue. These include epiglottal consonants.


1.[+/− advanced tongue root]: [+ATR] segments advance the root of the tongue.


2.[+/− retracted tongue root]: [+RTR] segments bunch the root of the tongue towards the pharyngeal wall and activate the pharyngeal constrictor muscles


[ GLOTTAL ] Purely glottal sounds do not involve the tongue at all. These are the glottal consonants.


The concept of a distinctive feature matrix to distinguish similar elements is identified with phonology, but there have been at least two efforts to use a distinctive feature matrix in