As the fourth volume of a multi-volume set on the Chinese language, this book studies the lexical system of Old Chinese and the development of different types of lexicons during the period. Focusing on lexicons in Old Chinese, the early form of the Chinese language used between the 18th century BCE and the 3rd century CE, this volume first introduces the methods of word formation in Old Chinese by analyzing words inscribed in oracle bones of the Shang Dynasty. Illustrated with examples, it then examines the lexical features of Old Chinese and explores the progress and evolutionary features of monosyllabic words, polysyllabic words, lexical meanings, synonyms, and idioms and proverbs over the course of the volume. This comprehensive groundwork on Chinese lexical history is a must-read for scholars and students studying ancient Chinese language, linguistics, and especially for beginning learners of the Old Chinese lexicon.