Primarily designed as a text for use on intermediate and advanced courses in English phonology, this book is aimed at those interested in recent developments in phonological theory. The discussion proceeds on the assumption that phonological differences between grammars, no less than syntactic differences, are constrained by universal principles and occur within fixed bounds defined by a relatively small number of parameters. The impact of this view on phonological theory is illustrated by analysis of a wide range of pronunication variables in English which offer insights into the limits of phonological variation. The book explores recent innovations in non-linear theory, focusing on the internal composition of segments and the manner in which these are organized into prosodic constituents. Phenomena discussed in connection with these developments include vowel length, weakening and vowel reduction, and syncope. A pivotal role is assigned to phonological licensing, which controls the ability of different positions in the prosodic hierarchy to support segmental contrasts.