This chapter considers the nature and history of the notion of the morpheme in linguistic analysis, and the suitability of that concept to linguistic analysis. The historical origins of the term are traced, especially as it was used in American Structuralist work, and a range of problems with the literal application of the traditional concept to actual languages sketched. The role played by a notion of morpheme in a range of recent theories is then outlined. It is argued that although the re-emergence of an interest in morphology in the 1970s brought with it an assumption that morphemes of a classical sort are the fundamental building blocks of the structure of words, the facts of actual languages argue for a rather different conception of the relation between the form and content of words from that grounded in their division into units of this sort.