An allomorph is a linguistics term for a variant form of a morpheme. The concept occurs when a unit of meaning can vary in sound (phonologically) without changing meaning. It is used in linguistics to explain the comprehension of variations in sound for a specific morpheme.
Allomorphy in English suffixes
English has several morphemes that vary in sound but not in meaning. Examples include the past tense and the plural morphemes.
For example, in English, a past tense morpheme is -ed. It occurs in several allomorphs depending on its phonological environment, assimilating voicing of the previous segment or inserting a schwa when following an alveolar stop:
- as /əd/ or /ɪd/ in verbs whose stem ends with the alveolar stops /t/ or /d/, such as 'hunted' /hʌntəd/ or 'banded' /bændəd/
- as /t/ in verbs whose stem ends with voiceless phonemes other than /t/, such as 'fished' /fɪʃt/
- as /d/ in verbs whose stem ends voiced phonemes other than /d/, such as 'buzzed' /bʌzd/
Notice the "other than" restrictions above. This is a common fact about allomorphy: if the allomorphy conditions are ordered from most restrictive (in this case, after an alveolar stop) to least restrictive, then the first matching case usually "wins". Thus, the above conditions could be re-written as follows:
- as /əd/ or /ɪd/ when the stem ends with the alveolar stops /t/ or /d/
- as /t/ when the stem ends with voiceless phonemes
- as /d/ elsewhere
The fact that the /t/ allomorph does not appear after stem-final /t/, despite the fact that the latter is voiceless, is then explained by the fact that /əd/ appears in that environment, together with the fact that the environments are ordered. Likewise, the fact that the /d/ allomorph does not appear after stem-final /d/ is because the earlier clause for the /əd/ allomorph takes priority; and the fact that the /d/ allomorph does not appear after stem-final voiceless phonemes is because the preceding clause for the /t/ takes priority.
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