An allomorph is a different phonological version of a morpheme. This occurs when the surface detail of the morpheme is different, but the deeper meaning remains the same. This commonly occurs when the letters performing the same function, such as plurality or time, produce a different sound or use different letters. Examples of plural allomorphs include the difference between ‘pots’ and ‘taxes.’ The studying of allomorphs is part of the studying of morphology in linguistics.
A morpheme is a basic unit of representing meaning in a language. These meanings can be either lexical, in that they provide information, or structural. Intolerant, for example, has three morphemes: in-toler-ant. All three elements of intolerant are lexical morphemes. ‘Toler’ is the root stem indicating the ability to endure or embrace something. The ‘in’ morpheme means that there is no tolerance and the ‘ant’ at the end indicates someone who is intolerant.
There are several types of morpheme. Free morphemes can exist as a word in their own right. An example of this is the break in unbreakable. On the other hand, morphemes such as ‘toler’ in tolerant are bound morphemes because they cannot exist unless modified by other morphemes. The allomorph is a bound morpheme that only occurs in order to modify a stem word.
The plural noun form is a common example used to explain an allomorph. Consider the difference in sound of the ‘s’ in ‘pots,’ ‘dogs’ and ‘taxes’ when spoken aloud. The ‘s’ in ‘pots’ sounds like a phonetic [-s], while the ‘s’ in ‘dogs’ is more of a phonetic [-z]. The ‘es’ of taxes, with the ‘e’ used to separate the ‘x’ and ‘s,’ is a phonetic [
Dative morphemes used with verbs can also become allomorphs. The regular past tense allomorph is ‘-ed.’ There is a difference in sound between ‘wanted,’ ‘fired’ and ‘dashed.’ Like with the plurals, each variation has a different sound while appearing to be the same on paper. The first is a phonetic [-ed], the second [d] and the third [t].
A regular allomorph can have different sounds. Irregular morphemes are also allomorphs. This means the irregular plural found in ‘sheep’ and ‘fish’ are also allomorphs of ‘s.’ This can occur through the merger of dialects, which produced ‘children.’ It can also occur when loan words are imported from another language such as with the difference between datum and data, both of which are from Latin.
Each allomorph is fixed in position. This means that one form, whether written or pronounced, can be replaced with another. For example, sheep will be the plural of sheep and will not be replaced with sheeps or sheepen. In language studies, such immovability is called ‘complimentary distribution.’