This is the first exhaustive investigation of gradience in syntax, conceived of as grammatical indeterminacy. It looks at gradience in English word classes, phrases, clauses and constructions, and examines how it may be recognized, defined, and differentiated. Bas Aarts considers the degree to which gradience is a grammatical phenomenon or a by-product of imperfect linguistic description, and makes a series of linked proposals for its theoretical formalization. His book will appeal to scholars and students of language and syntactic theory in departments of linguistics, philosophy and cognitive science.