This is an advance summary of a forthcoming article in the Oxford Research Encyclopedia of Linguistics. Please check back later for the full article.
Natural Morphology (NM) is a functionalist theory that aims to account for morphological preferences on the basis of extra-linguistic motivations. It is hierarchically structured in three (partially conflicting) sub-theories. The first sub-theory of universal naturalness (markedness) focuses on cognitive and semiotic principles such as transparency, iconicity, and bi-uniqueness, which are modeled in terms of parametric relations. Within the second sub-theory of typological naturalness, choices on the universal preference parameters are coordinated. The third sub-theory of language-specific naturalness elaborates what is normal in the potential system of a specific language. NM also puts special emphasis on the interface of morphology with other linguistic and non-linguistic components, thereby opening the new fields of morpho-pragmatics, morpho-notactics (as a special part of morphonology), and extra-grammatical morphology. A range of gradual clines are designed to assess not only transitions between adjacent components of grammar, but also within morphology between compounding, derivation, and inflection; and for notions such as regularity—sub-regularity—irregularity/suppletion, degrees of productivity, or of headedness. A double model of rivaling input-based productive dynamic morphology and of word-form-based stored static morphology is assumed within language-specific naturalness. Theoretical constructs are supported by ample external evidence, especially from diachrony and psycholinguistics.