Syncretism - where a single form serves two or more morphosyntactic functions - is a persistent problem at the syntax-morphology interface. It results from a 'mismatch', whereby the syntax of a language makes a particular distinction, but the morphology does not. This pioneering book provides the first full-length study of inflectional syncretism, presenting a typology of its occurrence across a wide range of languages. The implications of syncretism for the syntax-morphology interface have long been recognised: it argues either for an enriched model of feature structure (thereby preserving a direct link between function and form), or for the independence of morphological structure from syntactic structure. The Syntax-Morphology Interface argues for the autonomy of morphology, and the resulting analysis is illustrated in a series of formal case studies within network morphology. It will be welcomed by all linguists interested in the relation between words and the larger units of which they are a part.