Leishu

A leishu (類書; literally "categorized books") is a type of Chinese encyclopedic compilation, organized by categories or topics. Unlike dictionaries which focus on individual words, leishu compile extracts from a wide range of sources – histories, literary works, philosophical treatises, and more – under specific subject headings. They are essentially organized collections of excerpts, designed to provide researchers and scholars with readily accessible information on diverse topics.

Leishu served as valuable resources for scholars, particularly during the imperial examination era, as they offered comprehensive overviews of various subjects required for the exams. They were also employed as reference works for administrative officials and anyone seeking information on a vast array of topics, from rituals and customs to natural phenomena and historical events.

The format and scope of leishu can vary considerably. Some are relatively concise compendia, while others are massive multi-volume works. They often include summaries, annotations, and commentary alongside the original text excerpts. Prominent examples include the Yiwen Leiju (compiled during the Tang Dynasty) and the monumental Yongle Dadian (compiled during the Ming Dynasty). While the Yongle Dadian was never printed in its entirety, existing in manuscript form, its surviving fragments remain an invaluable resource for scholars today. The Gujin Tushu Jicheng (compiled during the Qing Dynasty) represents another significant leishu, notable for its comprehensive coverage and eventual publication.