There are several different things that a book titled The phonology of contrast could be about. Although contrast is widely held to play an important role in phonology, there is considerably less agreement as to exactly what kind of contrast is important, or what exactly that role is (see Hall 2011 for an overview and discussion). Some theories of contrast (e.g. Dresher 2009) posit a special status for features that serve to distinguish phonemes ; others (e.g. Flemming 2004) posit constraints that mandate perceptual distinctness in the phonetic realisation of contrasting segments.This book, revised and expanded from Kubowicz's dissertation (2003), focuses primarily on contrast at the level of the word, and explores cases of contrast transformation, in which words that contrast underlyingly in one property are mapped onto surface forms that differ in some other property, while the original contrast is neutralised. Kubowicz argues for what she calls PC (' preserve contrast ') theory, a version of Optimality Theory in which there are constraints specifically mandating the preservation of input contrasts (as distinct from traditional faithfulness constraints, which mandate the preservation of various properties of individual input forms). The theory is illustrated by application to three kinds of phenomena, each of which involves some form of opacity, a perennial problem for classic Optimality Theory. Chapter 2, which introduces most of the formal apparatus of the theory, looks at chain shifts, primarily in Finnish vowels, Chapter 3 deals with the interaction between epenthesis and stress in Arabic dialects and Chapter 4 presents an analysis of allomorph selection in Polish. These three case studies are bracketed by a brief introductory chapter, which outlines the premise and motivation of the theory, and a very brief conclusion.