Book excerpt: This book represents the state of the art in the study of gradience in grammar - the degree to which utterances are acceptable or grammatical, and the relationship between acceptability and grammaticality. Gradience is at the centre of controversial issues in the theory of grammar and the understanding of language. The acceptability of words and sentences may be linked to the frequency of their use and measured on a scale. Among the questions considered in the book are: whether such measures are beyond the scope of a generative grammar or, in other words, whether the factors influencing acceptability are internal or external to grammar; whether observed gradience is a property of the mentally represented grammar or a reflection of variation among speakers; and what gradient phenomena reveal about the relationship between acceptability and grammaticality, and between competence and performance. The book is divided into four parts. Part I seeks to clarify the nature of gradience from the perspectives of phonology, generative syntax, psycholinguistics, and sociolinguistics. Parts II and III examine issues in phonology and syntax. Part IV considers long wh-movement from different methodological perspectives. The data discussed comes from a wide range of languages and dialects, and includes tone and stress patterns, word order variation, and question formation. Gradience in Grammar will interest linguists concerned with the understanding of syntax, phonology, language acquisition and variation, discourse, and the operations of language within the mind.