Natural class
Encyclopedia
In phonology
, a natural class is a set of sounds
in a language that share certain phonetic
features
. The sound system of every language includes several natural classes, each distinguished from other classes by certain features. A given natural class is described using the minimum number of features needed to include all sounds within the class and exclude all sounds outside the class. Some natural classes in a language are larger and include several other natural classes within them, while some may be small and include only one speech sound. Natural classes tend to behave in similar ways, participating in the same phonological rule
s.
For example, the set containing the sounds /p/, /t/, and /k/ is a natural class in English, namely voiceless stops. This class contrasts with several other classes, such as the voiced stops, voiceless fricatives, sonorant
s, and vowel
s.
The class of voiceless stops is described by two features: [-continuant
] and [-voice
]. This means that any sound with both the feature [-continuant] (not able to pronounced continuously) and the feature [-voice] (not pronounced with vibration of the vocal chords) is included in the class. This correctly describes all voiceless stops and does not describe any sounds besides voiceless stops.
By implication, the class is also described as not having the features [+continuant] or [+voice]. This means that all sounds with either the feature [+continuant] (able to be lengthened in pronunciation) or [+voice] are excluded from the class. This excludes all natural classes of sounds besides voiceless stops. For instance, it excludes voiceless fricatives, which have the feature [+continuant], voiced stops, which have the feature [+voice], and liquid
s and vowel
s, which have the features [+continuant] and [+voice].
Voiceless stops also have other features, such as [+consonantal] and [-lateral], that are not added to the description of the class and are unnecessary, since the features [-continuant] and [-voice] already include all voiceless stops and exclude all other sounds.
In addition, members of a natural class will behave similarly in the same phonetic environment, and will have a similar effect on sounds that occur in their environment.
Phonology
Phonology is, broadly speaking, the subdiscipline of linguistics concerned with the sounds of language. That is, it is the systematic use of sound to encode meaning in any spoken human language, or the field of linguistics studying this use...
, a natural class is a set of sounds
Phoneme
In a language or dialect, a phoneme is the smallest segmental unit of sound employed to form meaningful contrasts between utterances....
in a language that share certain phonetic
Phonetics
Phonetics is a branch of linguistics that comprises the study of the sounds of human speech, or—in the case of sign languages—the equivalent aspects of sign. It is concerned with the physical properties of speech sounds or signs : their physiological production, acoustic properties, auditory...
features
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,...
. The sound system of every language includes several natural classes, each distinguished from other classes by certain features. A given natural class is described using the minimum number of features needed to include all sounds within the class and exclude all sounds outside the class. Some natural classes in a language are larger and include several other natural classes within them, while some may be small and include only one speech sound. Natural classes tend to behave in similar ways, participating in the same phonological rule
Phonological rule
A phonological rule is a formal way of expressing a systematic phonological or morphophonological process or diachronic sound change in language. Phonological rules are commonly used in generative phonology as a notation to capture sound-related operations and computations the human brain performs...
s.
For example, the set containing the sounds /p/, /t/, and /k/ is a natural class in English, namely voiceless stops. This class contrasts with several other classes, such as the voiced stops, voiceless fricatives, sonorant
Sonorant
In phonetics and phonology, a sonorant is a speech sound that is produced without turbulent airflow in the vocal tract; fricatives and plosives are not sonorants. Vowels are sonorants, as are consonants like and . Other consonants, like or , restrict the airflow enough to cause turbulence, and...
s, and vowel
Vowel
In phonetics, a vowel is a sound in spoken language, such as English ah! or oh! , pronounced with an open vocal tract so that there is no build-up of air pressure at any point above the glottis. This contrasts with consonants, such as English sh! , where there is a constriction or closure at some...
s.
The class of voiceless stops is described by two features: [-continuant
Continuant
A continuant is a sound produced with an incomplete closure of the vocal tract. That is, any sound except a stop or nasal. An affricate is considered to be a complex segment, composed of both a stop and a continuant.-See also:...
] and [-voice
Voice (phonetics)
Voice or voicing is a term used in phonetics and phonology to characterize speech sounds, with sounds described as either voiceless or voiced. The term, however, is used to refer to two separate concepts. Voicing can refer to the articulatory process in which the vocal cords vibrate...
]. This means that any sound with both the feature [-continuant] (not able to pronounced continuously) and the feature [-voice] (not pronounced with vibration of the vocal chords) is included in the class. This correctly describes all voiceless stops and does not describe any sounds besides voiceless stops.
By implication, the class is also described as not having the features [+continuant] or [+voice]. This means that all sounds with either the feature [+continuant] (able to be lengthened in pronunciation) or [+voice] are excluded from the class. This excludes all natural classes of sounds besides voiceless stops. For instance, it excludes voiceless fricatives, which have the feature [+continuant], voiced stops, which have the feature [+voice], and liquid
Liquid consonant
In phonetics, liquids or liquid consonants are a class of consonants consisting of lateral consonants together with rhotics.-Description:...
s and vowel
Vowel
In phonetics, a vowel is a sound in spoken language, such as English ah! or oh! , pronounced with an open vocal tract so that there is no build-up of air pressure at any point above the glottis. This contrasts with consonants, such as English sh! , where there is a constriction or closure at some...
s, which have the features [+continuant] and [+voice].
Voiceless stops also have other features, such as [+consonantal] and [-lateral], that are not added to the description of the class and are unnecessary, since the features [-continuant] and [-voice] already include all voiceless stops and exclude all other sounds.
In addition, members of a natural class will behave similarly in the same phonetic environment, and will have a similar effect on sounds that occur in their environment.