A detailed study of compound words in English, which analyses all aspects of their behaviour in the language This book makes two major contributions to our understanding of the formal grammar of English. One is the topic of compounding in English, and in particular the long-standing but unresolved research question of the difference between English compounds and phrases. The other is the theory of Lexicalism, the only version of Generative Grammar to have taken a serious interest in words and their structure. Bringing the two topics together, Heinz Giegerich shows that it is impossible to draw a dividing line between compounds and phrases, and therefore between the lexicon and the syntax, the two grammatical modules of Lexicalism; and he proposes a new model of grammatical modularity whereby the lexicon and the syntax overlap 'like slates on a roof'. This book will be of interest to all researchers and students with an interest in English linguistics or in morphological, syntactic or phonological theory.