The term is often applied to words that are difficult to classify according to traditional grammar.
[3]: p. 238 The first book devoted to the study of Chinese particles, 《語助》, was written by Lu Yi-Wei (盧以緯) in the period of the Yuan dynasty (1271–1368).
Later important works include 《助字辨略》 (Some Notes on the Helping Words) by Liu Qi (劉淇) and 《經傳釋詞》 (Explanations of the Articles Found in the Classics) by Wang Yin-Zhi (王引之), both published during the Qing dynasty (1644–1911).
The first work covering the particles found in the vernacular literature, 《詩詞曲語辭彙釋》 (Compilation and Explanations of the Colloquial Terms Found in Classical Poetry and Operas) by Zhang Xiang (張相), appeared posthumously in 1953.
[7] Written vernacular Chinese (白话; 白話; báihuà), refers to written Chinese that is based on the vernacular language used during the period between imperial China and the early 20th century.