The Erya is the oldest surviving Chinese dictionary and encyclopedic glossary, dating back to the 3rd century BCE. As a foundational text of the Confucian canon, it served to bridge the linguistic gap between archaic texts and the evolving language of the Han Dynasty. Unlike modern dictionaries organized by sound or radical, the Erya categorizes nearly 4,000 characters into 19 semantic chapters. By standardizing definitions for classical literature, the Erya became an indispensable tool for scholars and a precursor to the systematic study of Chinese lexicography.