Definition of the phoneme and its functions
To know how sounds are produced is not enough to describe and classify them as language units. When we talk about the sounds of language, the term "sound" can be interpreted in two different ways. First, we can say that [t] and [d], for example, are two different sounds in English: e.g. ten-den, seat-seed. But on the other hand, we know that [t] in let us and [t] in let them are not the same. In both examples the sounds differ in one articulatory feature only. In the second case the difference between the sounds has functionally no significance. It is clear that the sense of "sound" in these two cases is different. To avoid this ambiguity, linguists use two separate terms: phoneme and allophone.
The phoneme is a minimal abstract linguistic unit realized in speech in the form of speech sounds opposable to other phonemes of the same language to distinguish the meaning of morphemes and words (by Shcherba + Vassilyev).
Let us consider the phoneme from the point of view of its aspects.
Firstly, the phoneme is a functional unit. In phonetics function is usually understood as a role of the various units of the phonetic system in distinguishing one morpheme from another, one word from another or one utterance from another. The opposition of phonemes in the same phonetic environment differentiates the meaning of morphemes and words: e.g. bath-path, light-like. Sometimes the opposition of phonemes serves to distinguish the meaning of the whole phrases: He was heard badly - He was hurt badly. Thus we may say that the phoneme can fulfill the distinctive function.
Secondly, the phoneme is material, real and objective. That means it is realized in speech in the form of speech sounds, its allophones. The phonemes constitute the material form of morphemes, so this function may be called constitutive function.
Thirdly, the phoneme performs the recognitive function, because the use of the right allophones and other phonetic units facilitates normal recognition.
We may add that the phoneme is an abstract and generalized unit. The phoneme is a minimal language unit. The phoneme belongs to the language, the allophone – to the speech.
Language is an abstract category, it’s an abstraction from speech. Speech is the reality of a language, thus the phoneme as a language unit is materialized in speech sound. The phoneme is a sort of generalization (abstraction).
Let us consider the English phoneme /d/. It is an occlusive plosive stop, forelingual, apical, alveolar, lenis consonant. This is how it sounds in isolation or in such words as door, darn, down, etc, when it retains its typical articulatory characteristics. In this case the consonant [d] is called principal allophone.
The allophones which do not undergo any distinguishable changes in speech are called principal.
Allophones that undergo quite predictable changes under the influence of the neighboring sounds in different phonetic situations are called subsidiary, e.g.:
a) deal, did, did you - it is slightly palatalized before front vowels and [j];
b) bad pain, bedtime - it is pronounced without any plosion before another stop;
с) sudden, admit - it is pronounced with nasal plosion before [n], [m];
d) dry - it becomes post-alveolar followed by [r];
e) middle - before [l] a literal plosion;
f) breadth - before interdental sounds it becomes dental;
g) dwell - when followed by [w] it becomes labialized;
h) dead - in word final position it’s partly devoiced.
Thus, we see that the allophones mentioned above are all fore-lingual lenis stops, but they show some differences. The allophones of the same phoneme never occur in the same phonetic context.
Subsidiary allophones can be positional and combinatory. Positional allophones are used in certain positions traditionally. For example, the English /1/ is realized in actual speech as a positional allophone: it is clear in the initial position, and dark in the terminal position, compare light, let and hill, melt. Russian positional allophones can be observed in вопль, рубль where terminal /л/ is devoiced after voiceless /п, б/.
Combinatory allophones appear in the process of speech and result from the influence of one phoneme upon another.
Native speakers do not observe the difference between the allophones of the same phoneme. At the same time they realize that allophones of each phoneme possess a bundle of distinctive features that makes this phoneme functionally different from all other phonemes of the language. This functionally relevant bundle is called the invariant of the phoneme. All the allophones of the phoneme /d/ are occlusive, forelingual, lenis. If occlusive articulation is changed for constrictive one [d] will be replaced by [z]: e. g. breed - breeze, deal — zeal.
Thearticulatory features which form the invariant of the phoneme are called distinctive or relevant.
To extract relevant features of the phoneme we have to oppose it to some other phoneme in the phonetic context.
If the opposed sounds differ in one articulatory feature and this difference brings about changes in the meaning this feature is called relevant: for example, port — court, [p] and [k] are consonants, occlusive, fortis; the only difference being that [p] is labial and [t] is lingual.
The articulatory features which do not serve to distinguish meaning are called non-distinctive, irrelevantorredundant. For example, it is impossible to oppose an aspirated [ph] to a non-aspirated one in the same phonetic context to distinguish meaning.
We know that anyone who studies a foreign language makes mistakes in the articulation of sounds. L.V. Shcherba classifies the pronunciation errors as phonological and phonetic. If an allophone is replaced by an allophone of a different phoneme the mistake is called phonological. If an allophone of the phoneme is replaced by another allophone of the same phoneme the mistake is called phonetic.