Distinctive feature

In linguistics, a distinctive feature is the most basic unit of phonological structure that may be analyzed 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 1950's, features traditionally have been specified by assigning them binary values to signify that the segment being described by the feature either possesses that phonetic property or it does not. Therefore, a positive value, [+], denotes the presence of a feature, while a negative value, [-], indicates its absence. However, in recent developments to the theory of distinctive features, phonologists have proposed the existence of single-valued features. These features, called univalent features, can only describe the classes of segments that are said to possess those features, and not the classes that are without them.

Major Class Features: The features that represent the major classes of sounds.
 * 1) [+/- consonantal] Consonantal segments are produced with an audible constriction in the vocal tract, like plosives, affricates, fricatives, nasals, laterals and [r]. Vowels, glides and laryngeal segments are not consonantal.
 * 2) [+/- sonorant] This feature describes the type of oral constriction that can occur in the vocal tract. [+son] designates the vowels and sonorant consonants, which are produced without the imbalance of air pressure in the vocal tract that might cause turbulence. [-son] alternatively describes the obstruents, articulated with a noticeable turbulence caused by an imbalance of air pressure in the vocal tract.
 * 3) [+/- syllabic] Syllabic segments may function as the nucleus of a syllable, while their counterparts, the [-syll] segments, may not.

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 wide 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. [-cg] implies the opposite.

Manner Features: The features that specify the manner of articulation.
 * 1) [+/- continuant] Continuant features describe the passage of air through the vocal tract. [+cont] segments are produced without any significant obstruction in the tract, and so air passes 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 passages 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 that 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 [+dr].

Place Features: The features that specify the place of articulation.
 * [ LABIAL  ] Labial segments are articulated with the lips.
 * 1) [+/- round] [+round] are produced with lip rounding. [-round] are not.
 * [ CORONAL] Coronal sounds are articulated with the tip and/or blade of the tongue.
 * 1) [+/- anterior] Anterior segments are articulated with the tip or blade of the tongue at or in front of the alveolar ridge.
 * 2) [+/- distributed] For [+dist] segments the tongue is extended for some distance in the mouth.
 * [ DORSAL ] Dorsal sounds are articulated by raising the dorsum of the tongue. All vowels are DORSAL sounds.
 * 1) [+/- high] [+high] segments raise the dorsum close to the palate. [-high] segments do not.
 * 2) [+/- low] [+low] segments bunch the dorsum to a position low in the mouth.
 * 3) [+/- back] [+back] segments are produced with the tongue dorsum bunched and retracted slightly to the back of the mouth. [-back] segments are bunched and extended slightly forward.
 * 4) [+/- tense] This feature (mainly) applies to the position of the root of the tongue when articulating vowels. [+tense] vowels have an advanced tongue root. In fact, this feature is often referred to as Advanced tongue root, though there is a debate on whether tense and ATR are same or different features.
 * [ RADICAL ] Radical sounds are articulated with the root of the tongue.