A variant of a morpheme which occurs in certain definable environment. It is an important concept that is necessary in the determination of the plural, past tense and possessive inflections in morphology.
Allomorphs are conditioned either phonologically or morphologically.
An allomorph is phonologically conditioned when the form of the allomorph at any given time is dependent on the adjacent phonemes. The two major examples in English are: a) The plural morpheme b) The past tense morpheme c) To a very reasonable extent the indefinite article and the possessive morphemes.
The three regular variants of the plural morpheme are: [әz], [z] and [s]. The three variants are realised in the following phonetic environment. i.
[әz] when the plural morpheme comes after sibilants that is, whistling fricatives and affricates such as -/s/ /z/ /ʃ/ /ʒ/and /ʧ/ /ʤ/ as in the plural forms of the words buzz, garage, judge, house, rich, splash when pronounced or transcribed. ii.
[z] when the plural morpheme comes after all voiced sounds except voiced fricatives and affricates as indicated in (i) above as in the plural forms of the words-dog, lady, arm, good, bee, boy. iii.
[s] when the plural morpheme comes after voiceless sounds except voiceless fricatives and affricates as in (i) examples are the plural forms of the following wordscat, kick, laugh, cap, chemist.
The past tense morpheme also has three variants. They are: [әd], [d] and [t]. i.
[әd] When the past tense morpheme comes after a verb ending with the alveolar plosives /t/ and /d/ as in the words-want, wait, bend, hand, load, part. ii.
[d] when the past tense morpheme comes after verbs ending with other voiced sounds apart from /d/ as in the words – stab, bath, open iii.
[t] occurs after verbs ending with voiceless sounds except /t/ as in the following examples-stop, jump, push, work and walk.
The possessive morpheme also takes the same forms as the plural morphemes except for the following moderations or modifications: the possessive form is marked in English by adding an apostrophe and an ‘s’ to singular nouns as in boy’s, king’s and an apostrophe without an
‘s’ to plural nouns as in ‘the teachers’ idea’.
In the case of the neuter third person singular pronoun, the possessive form is realised as ‘its’ and not as ‘it’s’ as one would have normally expected giving the general rule.
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The indefinite article in English is also phonologically conditioned because the choice between ‘a’ and ‘an’ is determined by whether the noun following begins with a consonants or a vowel.
As we can see from the different examples, the allomorphs of a morpheme are in complementary distribution, meaning that they are mutually exclusive such that where one occurs the other does not occur. In other words, they cannot substitute for each other.
Allomorphs are also governed by morphophonemic rule, that is, a rule which has the form of a phonological rule, but is restricted to a particular morphological environment.
Morphophonemic rules are sensitive to their environment. Whenever morphological information is required to specify the environment for an allophonic rule, the rule is morphophonemic as in the prefix /in-/ having the allomorphs [im], [il] and [ir] in words such as impossible, illogical and irregular.
MORPHOLOGICAL CONDITIONING
This is required for allomorphs which do not depend on actually spoken neighbouring sounds. In other words, the selection is determined by the specific morpheme or morphemes forming the context. Morphological conditioning applies to irregular plural and past tense forms in English. These irregular cases are often referred to as suppletive forms and they constitute a small set of lexical items in English. The following are examples: i.
The Zero Affixation
This process is used to describe nouns which have their singular forms changed into the plural without any change in the phonological representation as in sheep, property , furniture , deer , cattle and information.
ii.
Pluralization by Replacement and Internal Change
This process applies to words such as goose, man, woman, foot with their plurals as geese, men, women and feet respectively. Morphological conditioning also explains the following formsox/oxen, fox/foxes, child/children.
Another example of morphological conditioning is the changes that verb undergoes in words like go-went-gone; sing-sang-sung; deal-dealt-dealt.
The concept of allomorphs and how they can be phonologically and morphologically conditioned are further evidence that the process of affixation performs grammatical functions in language because of their structural roles in the formation and patterning of acceptable syntactic sequences.
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