In English there are many cases when a phoneme or phonemes within the morpheme may be replaced by another phoneme or other phonemes. These substitutions of phonemes may or may not be determined by a certain position of stress. The position of stress may also vary in different word derivates formed from one base morpheme. The substitution of phonemes by one another and the change of the position of stress within morphemes are called phoneme and stress alternations. Theory of phoneme alternations suggested by LA. Bedouin de Courtenay was very important in further development of linguistics. It has contributed to the formation of a new branch of linguistics — «morphonology» (or «morphophonology», «morphophonemics») which is defined differently by various linguists. In the formation of morphonology much credit goes to N. S. Trubetzkoy who defined it as (1) a part of word phonology which studies the phonological structure of moiphemes, as (2) a division of grammar, as (3) a linking branch between morphology and phonology. Among these definitions the first and the third can be accepted. Morphonology has not got its own unit, though some linguists introduced the term «morphoneme» which does not exist at all. Morphonology uses the terms phoneme and morpheme borrowed from other linguistic levels and studies phoneme and stress alternations, performing morphonological functions. The other aspects of morphonology, which study the phonological structure of morphemes and combinatory sound changes occurring in some morphemes, are not studied in morphonology. In recent theories not all the alternations taking place within morphemes are included in morphonology, though some linguists, especially American scholars, regard it is being |so. Morphonology does not include the description of suppletion or pormanteau morphemes (e. g. good — better — best), internal inflexion, i.e. the changes in the base of a word or base morphemes distinguishing grammatical forms (e. g. write — wrote, ox — oxen, foot — feet, beet — bet), alternations in the affixes which occur under the certain phonetic conditions .
Phonetic alternations include changes under assimilation, e. g. the Present Tense third person singular suffix (-s, -iz, -z) variation which depend on the position: cats /kaets/, boxes /boksiz/, bags /baegz/.
Historical alternations take place in words etymologically related, e. g. in the verbs: sing — sang — sung, bend — bent, begin — began, build — built, choose — chose, lose — lost; in the nouns formed by internal inflexion: goose — geese, foot — feet, mouse — mice, woman — women and in other words as hot — heat, breathe — breath, gold — gild, child — children1. In the latter ex ample there are alternations both in base and affix.
Alternations performing morphological (grammatical) functions, which serve to distinguish different grammatical forms of words, are called morphonological alternations. They are frequently used in the Slavic languages. The morphonological alternations used in different languages have not been studied thoroughly, but they are of great theoretical value for modern linguistics. Morphonology may clarify the relationship between base and affixal morpheme and their different variations in word formation. Morphonological structure of a language shows how phonology works to transform morphological units'.
The unity of morphemes, the identity of different variants of the morpheme (or «allomorphs») to be more precise, is deter mined of their phonological identification which is their formal but not functional-semantic side.
Explaining phoneme and stress alternations, we have defined their morphonological aspect. It must be emphasized that the morphonological aspect of phoneme and stress alternations may be studied independently as a «bridge» linguistic level between phonology and morphology.
Variations of the formal structure of English morphemes may take place, owing to phonemic and accentual distinctions. As the morpheme is a meaningful unit of a language, it may be used as a word, if it is a monomorphemic word, or as a part of a word, if it is a composite word. Usually morphonological alternations occur in composite words, between their morpheme boundaries or within a morpheme, e. g. Neptune /'neptju:n/ — Neptunian /nep'tjumian/, placid /'plasid/, placidity /pla'siditi/, fruit /fru:t/ — fruitarian /fru: teanan/, plastic /'plastik/ — plasticity /plas'tisiti/, plural /plural/ — plurality /plu'raeliti/, anile /'enail/ — anility /a 'niliti/ in the latter case there are two phonemic alternations and one stress alternation, Some linguists include morphonological alternations into lexicology or morphology due to their active part in word-building or changing the grammatical | forms of morphemes.
Like other linguistic levels, morphonology is determined para-digmatically, i.e. the members of alternation may be distinguished as phonologically distinctive units — phonemes, and syntagmatically, i.e. the alternations take place in certain position which do not depend on the context or other factors.
Besides, the suffix -ion influences in such a way as to change different vowel and consonant phonemes within a word. Such different alternations, causing changes of phonemes in the phonetic structure of a word, may be orbserved in the variations of other suffixes'.
English is regarded a language in which monosyllabism is typical. There is a small number of productive suffixes in English, some of which consist of a single consonant or consonant clusters. The variations of morphemes performing morphological functions and formal structure of morphemes, being the object of morphonology, should be studied in close relationship with affixation in word-building.
Russ i is rich in morphonological alternations: da ка -ручной, сухой — сушить, орех — орешник, доска — дощечка, заяц- зайцы.
Some morphonological alternations occur in Uzbek too: past «low» — pasaymoq «to be low» sust «weak», susaymoq «to weaken», ulug' «great» — ulg'aymoq «to be great», son «number» — sanoq «counting», o'qi «read», o'quv «reading».
A kind of prefexation in reduplication of an initial syllable with one of the consonants, frequently with /p, s, r, m/, occur in Turkish2 and Uzbek, probably, in other Turkic language as well, e. g. in Turkish sap-sari, in Uzbek sap-sariq (extra-yellow),' in Turkish dos-dogru, in Uzbek to'p-to'g'ri or to'ppa-to'g'ri (Very correct), in Turkish bem-beyar, in Uzbek oppoq (extra-white). In compounding, some alternations occur at the junctural border of morphemes, e. g. no one /n n/, Uzbek: bu kun — bugun «to-day».
An adequate morphonological description of alternations may contribute to establishing some internal phenomenon of a language, which has theoretical and practical value in general linguistics
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