This book deals with one of the central problems for theories of word-formation, the productivity of morphological processes. A broad range of English derivational affixes are investigated, making use of recent innovations in lexicography, quantitive corpus linguistics, Optimality Theory and Lexical Conceptual Semantics. It is argued that the productivity of a given affix and its combinability with other affixes are primarily the result of its individual structural properties (phonological, morphological and semantic), and not due to more general mechanisms of the various kinds proposed, for example, by proponents of Lexical Phonology/ Morphology or Lexeme-Morpheme-Base Morphology.