Language change is operative at all levels of a language. Alongside the effects of general linguistic change phenomena, word formation displays a species of change all its own. A central concern of this study is to delimit and describe this specific species. A theoretical definition of the subject addressed by the study leads on to an evaluation of authentic language material. It transpires that word-formation change is centrally determined by changes in linguistic productivity, empirically substantiated here by the analysis of newspaper texts from the 17th to the 20th century.