There have been many variations on these themes. The US linguist Dwight Bolinger (Aspects of Language, 1968) divided Bloomfield's morpheme into a system morpheme (the glue) and a source morpheme (the lexical content), while the French linguist André Martinet (Éléments de linguistique générale, 1970) subsumed Vendryes's morpheme and lexeme under a unifying unit the moneme. In this approach, the specimen sentence has 13 monemes divided into 8 morphemes and 5 lexemes. Currently, whatever the terms used, linguists tend to agree on three points: (1) Grammatical and lexical units need to be distinguished: for example, the two elements cat and s in the word cats are different aspects or levels of language. (2) Not all the features in a stretch of language are physically realized: for example, cats may exhibit a marker of plurality, but sheep does not. (3) One unit of form may serve more than one end: for example, were in the specimen sentence above combines BE and past. The traditional structuralist approach assumes that all the morphemes of a language can in principle be listed in a morpheme inventory, like a PHONEME inventory, but because of the complexities involved, few such lists have been attempted and none exists for English.
In later STRUCTURAL LINGUISTICS, the morpheme has been defined as the abstraction behind a morph (a form that has semantic distinctiveness). It may subsume two or more allomorphs, morphs that have common semantic identity but differ in their pronunciation according to well-defined rules: for example, the prefixes in-, im-, il- are allomorphs of the same morpheme (in this case a negative prefix) in the words insincere, impolite, illogical, the choice of prefix being determined by the initial sound of the stem that follows the prefix. When it deals with morphs and morphemes, morphology is known as morphemics. See -EME, LEVEL OF LANGUAGE.
mor·pheme / ˈmôrˌfēm/ • n. Linguistics a meaningful morphological unit of a language that cannot be further divided (e.g., in, come, -ing, forming incoming). ∎ a morphological element considered with respect to its functional relations in a linguistic system.DERIVATIVES: mor·phe·mic / môrˈfēmik/ adj.mor·phe·mi·cal·ly / môrˈfēmik(ə)lē/ adv.