Tuan Yü-ts'ai 段玉裁 (T. 若膺 H. 茂堂, 硯北居士, 長塘湖居士, 僑吳老人), 1735-1815, scholar, etymologist and phonetician, was a native of Chin-t'an, Kiangsu. His father, Tuan Shih-hsü<> 段世續 (T. 得莘, 1710-1803), made his living by teaching. For several years, beginning in 1745, Tuan Yü-ts'ai studied under his father in Wu-chin, Kiangsu, where the latter had a teaching position. After becoming a chü-jên (1760) he went to Peking. There he read for the first time the Yin-Hsüeh wu-shu by Ku Yen-wu [q.v.] and began to take an interest in the study of phonetics. Failing to pass the metropolitan examination in the following year (1761), he accepted a position as teacher in the government school for children of the three highest Banners, located in the Wan Shan Tien 萬善殿 at Ching-shan 景山 in the Forbidden City. He remained at this post until 1767. When the eminent scholar, Tai Chên [q.v.], came to Peking in 1763 Tuan and a group of several other scholars met with Tai to discuss matters of current intellectual interest. Thus Tuan Yü-ts'ai became, and remained throughout his life, a devoted disciple of that master. Upton relinquishing his teaching post in 1767 he and his younger brother, Tuan Yü-ch'êng 段玉成 (T. 器之 b. 1737, chü-jên of 1786), went home where the two worked together on the Classic of Poetry. As a result of this study Tuan Yü-ts'ai produced two short phonetical studies, entitled 詩經均譜 Shih-ching yün-p'u and Ch'ün 羣 ching yün-p'u, which served as the basis of his later work on ancient phonology known as 六書音均表 Liu-shu yin-yün piao (see below). He returned to Peking in the spring of 1769 to compete in the metropolitan examination. Being unsuccessful, he accompanied Tai Chên to Shansi where Chu Kuei [q.v.] was officiating as financial commissioner. While Tai was compiling the gazetteer of Fenchow, Shansi (1769), Tuan lectured at the Shou-yang 壽陽 Academy, some three hundred li northeast of Fenchow.
In 1770 Tuan Yü-ts'ai became magistrate of Yü-p'ing, Kweichow. Dismissed two years later  for some error in administration, he went in the autumn of 1772 to Szechwan as an expectant magistrate. There he served twice as acting magistrate of Fu-shun (1772-74 and 1775-76), as well as at Nan-chi (1774) and at Wu-shan (1778). In 1775 he completed the above-mentioned Liu-shu yin-yün piao which classifies the ancient sounds into seventeen groups. In the same year he compiled the local history of Fushun, 富順縣志 Fu-shun hsien-chih, his postscript to the work being dated 1777. In 1780 he retired from official life on the plea of ill health. On his way home in 1781 he visited Ch'ien Ta-hsin [q.v.] at the Chung-shan Shu yüan in Nanking. In 1791 he completed a work on the Classic of History, entitled 古文尚書撰異 Ku-wên Shang-shu chuan-i, in 32 chüan, in which he analyzes the form and meaning of difficult characters in the so-called ancient text of the Classic of History-a forged document of antiquity which had suffered by frequent reediting, sometimes at the hands of incompetent scholars (see under Yen Jo-chü). At this juncture he was compelled, on account of a law-suit over his family's ancestral tombs, to transfer his residence, in 1792, from Chin-t'an to Soochow. About this time, too, he re-edited and expanded to 12 chüan the literary works of his teacher, Tai Chên. That collection, entitled Tai Tung-yūan Hsien-shêng ch'üan-chi (see Tai), was printed in 1793.
The chief contribution of Tuan Yü-ts'ai to classical and etymological studies was his analysis of the characters in the ancient dictionary, 說文解字 Shuo-wên chieh-tzŭ (commonly referred to as Shuo-wên) by Hsü<> Shên 許慎 (T. 叔重), which was completed in 100 A.D. and presented to the throne by his son, Hsü<> Ch'ung 許沖, in 121 A.D. It is the earliest extant dictionary on the origin and formation of Chinese characters, and scholars of the Ch'ing period found it helpful in the understanding of difficult texts. In the Sung period the brothers, Hsü<> Ch'ieh (see under Fêng Kuei-f ên) and Hsü<> Hsüan (see under Yen K'o-chün), each made an improved edition of the Shuo-wên chieh-tzŭ, but Tuan Yü-ts'ai was the first scholar of modern times to make a thorough study of all the works relating to it. He began by collating Mao I's [q.v.] reprint of Hsü<> Hsüan's edition, which was the only one then in wide circulation, comparing it with the Sung and Ming editions, mostly rare manuscripts in the possession of Chou Hsi-tsan and Yüan T'ing-t'ao (for both see under Ku Kuang-ch'i). His notes on this collation he embodied in the work 汲古閣說文訂 Chi-ku ko Shuo-wên ting, 1 chüan, printed in 1771, revised and reprinted in 1772. It was later criticized by Yen K'o-chün [q.v.] under the title, Shuo-wên ting-ting. In 1807 he completed his annotations to the Shuo-wên and printed them in 1813-15 under the title Shuo-wên chieh-tzŭ chu (註), 30 chüan. The entire dictionary was thus annotated, giving corrections, emendations, and additions. The importance of his work, and the amount of interest it aroused, is certified by the large number of supplementary studies prepared by other scholars. The more ambitious of this type are the 說文段注訂補 Shuo-wên Tuan-chu ting-pu, 14 chüan (1888), by Wang Shao-lan 王紹蘭 (T. 畹馨 H. 南陔, 1760-1835); the Shuo-wên Tuan-chu k'ao-chêng (see under Fêng Kuei-f ên); and the Tuan-shih Shuo-wên chiao-ting, by Niu Shu-yü<>[q.v.]. Minor supplements in the same field are the Shuo-wên Tuan-chu ch'ao-an (抄按), by Kuei Fu (see under Chou Yung-nien); the Shuo-wên Tuan-chu cha-chi (札記), by Hsü<> Sung [q.v.], and another with the same title by Kung Tzŭ-chên [q.v.], Tuan's grandson.
Among other etymologists who commented on Tuan's work, the following may be mentioned: Wang Nien-sun [q.v.], whose Tuan-shih Shuo-wên ch'ien-chi (簽記), was reproduced from a manuscript and included in the collectanea, 稷香館叢書 Chi-hsiang kuan ts'ung-shu (1935); Chu Chün-shêng 朱駿聲 (T. 豐艹巳 H. 允倩, 石隱, 1788-1858), whose Shuo-wên Tuan-chu nien-wu (拈誤), was reproduced in the same collectanea; Hsü<> Ch'êng-ch'ing 徐承慶 (T. 謝山), whose Shuo-wên Tuan-chu k'uang-miu (匡謬), 8 chüan, was printed in the Chih-chin chai ts'ung-shu (see under Yao W ên-tien); Hsü<> Hao 徐灝 (T. 子遠 H. 靈洲 1810-1879), whose Shuo-wên Tuan-chu chien (箋), was printed in 1894 and reprinted in 1914; and Tsou Po-ch'i (see under Li Shan-Ian). The above-mentioned Kuei Fu, a native of Ch'u-fu, Shantung, was less arbitrary than Tuan in his approach to the study of the Shuo-wên at doubtful points he left more for the reader to decide. His Shuo-wên chieh-tzŭ i-chêng (義證), 50 chüan, was printed in 1851. He influenced two other natives of Shantung working in the same field, namely Hsü<> Han 許瀚 (T. 印林, chü<> jên of 1835) and Wang Yün 王筠 (T. 貫山 H. 菉友, 1784-1854).
Tuan Yü-ts'ai printed his own works from time to time, under the collective title, 經韻樓叢書 Ching-yün lou ts'ung-shu. This ts'ung-shu contains, among other items, a collection of his essays, Ching-yün lou chi (集), in 12 chüan.  Also included are two works by his teacher, the afore-mentioned Tai Chên, and a chronological biography of Tai, entitled Tai Tung-yüan h sien-shêng nien-p'u, which Tuan compiled.
Tuan Yü-ts'ai had two sons and one daughter. The daughter, Tuan Hsün 段馴 (T. 淑齋, author of a collection of verse, entitled 綠窗吟榭詩草 Lü-ch'uang yin-hsieh shih-Ts'ao, was the wife of Kung Li-chêng (see under Kung Tzŭ-chên).
[ 1/487/21a; 2/68/53a; 6/39/2b; 20/3/00 (portrait); Chin-t'an hsien-chih (1885) 9/15a; Liu P'an-sui, Tuan Yü-ts'ai Hsien-shêng nien-p'u in Tsing hua hsüeh-pao, vol. 7, no. 2; Edkins, J., Introduction to the Study of Chinese Characters (1876) pp. 170-71.]