Negation is at the core of human Language; without negation there can be no denial, contradiction, irony, or lies. This book examines the form and function of negative sentences in a variety of Languages and offers state-of-the-art surveys of the acquisition of negation by children, its processing by adults, its historical development, and its interaction with other operators and predicates within natural Language sentences. Topics covered include the nature of negative polarity, the phenomenon of pleonastic or illogical negation, and the role of morphological, syntactic, semantic, pragmatic, and typological factors in negative expression.