This book explores the empirical and theoretical aspects of constituent structure in natural language syntax. It surveys a wide variety of functionalist and formalist theoretical approaches, from dependency grammars and Relational Grammar to Lexical Functional Grammar, Head-driven Phrase Structure Grammar, and Minimalism. It describes the traditional tests for constituency and the formal means for representing them in phrase structure grammars, extended phrase structure grammars, X-bar theory, and set theoretic bare phrase structure. In doing so it provides a clear, thorough, and rigorous axiomatic description of the structural properties of constituent trees. Andrew Carnie considers the central controversies on constituent structure. Is it, for example, a primitive notion or should it be derived from relational or semantic form? Do sentences have a single constituency or multiple constituencies? Does constituency operate on single or multiple dimensions? And what exactly is the categorial content of constituent structure representations? He identifies points of commonality as well as important theoretical differences among the various approaches to constituency, and critically examines the strengths and limitations of competing frameworks. This is an ideal introduction for graduate students and advanced undergraduates. It is also a valuable reference for theoretical linguists of all persuasions in departments of linguistics, cognitive science, computational science, and related fields.