Morphology - Unit Two - Lesson No. 12
Allomorphs are phonologically distinct variants of the same morpheme. By phonologically distinct , we mean that they have similar but not identical sounds. And when we say that they are variants of the same morpheme , we mean that those slightly different-sounding sets of forms share the same meaning or function. For example, the negative prefix ( in- ) in English is often pronounced in- (as in intolerable ), but is also sometimes pronounced im- or –il ( impossible, illegal ), as English spelling shows (although English spelling is not a reliable guide for pronunciation). Since all of these forms still mean ‘negative’, and they all attach to adjectives in the same way, we say that they are allomorphs of the negative prefix. Similarly, the plural morpheme in Turkish sometimes appears as –lar and sometimes as –ler :
So Turkish has two allomorphs of the same morpheme, (Lieber 2009: 158).
Is every morpheme pronounced the same in all contexts? If it were, most phonology texts could be considerably shorter than they are. In fact, many morphemes have two or more different pronunciations, called allomorphs, the choice between them being determined by the context. These include some of the commonest morphemes in the language (English).
For example, the English plural morpheme has three different pronunciations:
The –s suffix has three allomorphs: [s] as in cats, [Z] as in dogs or days, and [IZ] or [əz] as in horses or judges.
The three allomorphs are distributed in an entirely regular fashion, based on the immediately preceding the suffix, thus:
Another very common suffix with phonologically determined allomorphs is the one spelled –ed, used in the past tense form of most verbs. Its allomorphs are [t], [d] and [id] or [ɪd]. The distribution of the past tense allomorphy in English can be stated in the following simple rule:
The second and the third conditions are the same as for the plural –s, only the first is different, (Carstairs-McCarthy, 2002: 124-5).