"A universal property of natural language is that every language is able to express negation. However, languages may differ to quite a large extent as to how they express this negation. Not only do languages vary with respect to the form of negative elements, the position of negative elements is also subject to cross-linguistic variation. Moreover, languages differ in terms of the number of manifestations of negative morphemes too: in some languages negation is realized by a single word or morpheme, in other languages by multiple morphemes, a phenomenon known as Negative Concord. Moreover, the syntax and semantics of negation is indissolubly connected to the phenomenon of negative and positive polarity. Negative Polarity Items (NPIs) are items, like English ever, whose distribution is limited to a number of contexts, which in some sense all count as negative. Positive Polarity Items (PPIs) form the mirror image of NPIs. These are elements, such as English rather, that are banned from appearing in negative sentences. In this book I present an overarching perspective on negation and negative dependencies, based on novel data from language variation, language acquisition and language change. In this book I develop and explore the hypothesis that, to the extent that they are applicable to the domain of negation, all known syntactic, semantic, pragmatic and lexical ways of encoding dependencies should be attestable in the domain of negation as well, unless they are ruled out independently (e.g. on functional, formal or learnability grounds). This hypothesis predicts a pluriform landscape of all kinds of negative dependencies and markers of negation, a prediction that I will show is born out"--