This is the first monograph-length volume entirely devoted to the theoretical and empirical issues raised by the definition of ‘word’ and related concepts in Arabic, both at the historical and synchronic level. Some of the best-known scholars in the field of Arabic linguistics debate such issues as the technical definition of words and morphemes in the Arabic grammatical and rhetorical traditions, the theoretical status of the root and its interactions with morphology, the analysis of word in the computer treatment of Arabic texts, some relevant phenomena in the contact of Arabic with other languages. The result is a fresh portrait of some of the most interesting research currently under way in Arabic linguistics from different theoretical and methodological viewpoints.