Genetics is one of the most rapidly advancing of the life sciences. This growth is accompanied by a proliferation in terminology, which constitutes a problem to the student and professional alike. Many of the words, especially those from molecular genetics, are newly coined. Other words, like those used in quantitative genetics or mutational studies, are from non-biological fields, such as statistics or physics. The text and journal reader is referred to the scientific names of species and genera, often without knowing whether the organism is a grass, an insect, or a rodent. The fourth edition of Dictionary of Genetics , containing more than 6,000 entries, will continue to be the definitive reference for students of classical and molecular genetics. In addition to the most current account of terminology available, this edition includes four newly updated appendices giving a chronology of events bearing on genetics, a list of professional journals, a classification of organisms, and a list of domesticated species.