 Morphs are the basic building blocks of words. They are classified as allomorphs if they have the same grammatical function within a word and thus constitute a family. Let us illustrate that. Here are three nouns, horse, dog and cat, with their phonemic representation. Their plural forms, which are identical orthographically, involve three different morphs, is, z and s. But they all have the same function. They denote the plural form of the noun to which they are attached. Thus they are members of a family of morphs that vary in sound but not in function. Such family members are referred to as allomorphs and their head term is referred to as the morpheme. Morphs, allomorphs and the morpheme itself are all represented within curly brackets. In fact, the allomorphs of a morpheme can often be determined by a phonological rule. Take the plural morpheme in present-day English and its allomorphs. The voiced z occurs after voiced phonemes, that is, after vowels and voiced consonants. The voiceless s occurs after voiceless consonants and the morph is occurs after s, z, z and s. And in terms of distinctive features, after continuing coronals that have the feature sonorant.