Book excerpt: This book provides hands-on experience with a major area of modern phonology, including phonetics; phonetic variation; natural classes of sounds; alternations; rule systems; and prosodic phonology. Working with problems is an essential part of courses that introduce students to modern phonology. This book provides hands-on experience with a major area of modern phonology, including phonetics; phonetic variation; natural classes of sounds; alternations; rule systems; and prosodic phonology. An introductory essay gives an overview of some of the principal results and assumptions of current phonological theory. The problems are taken from a wide variety of languages, and many are drawn from the authors' firsthand research. All have been used by the authors in their introductory courses, primarily at Harvard and MIT, and are meant to be used in conjunction with a textbook and/or other materials provided by the classroom instructor.