Grammatical particles, or simply particles, are words that convey certain grammatical meanings. The term is often applied to words that are difficult to classify according to traditional grammar.^[1] Both Classical Chinese and Modern Standard Chinese make use of particles. In Chinese, particles are known as zhùcí (simplified Chinese: 助词; traditional Chinese: 助詞) or yǔzhùcí (语助词; 語助詞). They belong to function words (虚词; 虛詞; xūcí). In other words, they have no lexical meaning, but are used to indicate certain grammatical information. This contrasts with content words (实词; 實詞; shící).^[2] Particles in Chinese usually take the neutral tone.^{[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). These works focus on particles in the Confucius classics. Particles used in the vernacular literature did not draw much attention. 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.

Linguists often categorise Chinese particles into the following types:

• Structural particle (结构助词; 結構助詞; jiégòu zhùcí):^[4] This class of particles concern syntactic relations. The particles can be distinguished only in written form because they are usually pronounced the same.
  • 地(dì/de) is used to mark adverbials (狀語). E.g.: 安靜地睡著了 (ānjìng dì/de shuì zháo le) 'fell asleep quietly'
  • 得(dé/de) is used to mark verb complements (補語). E.g.: 學習得很認真 (xuéxí dé/de hěn rènzhēn) 'study very hard'
  • 的(dè/de), according to traditional analysis, is used to mark attributive (定語). It is often analysed as a nominaliser.^[5] E.g.: 書的封面很漂亮 (shū dè/de fēngmiàn hěn piàoliang) '(the) cover of the book (is) very beautiful'

• Aspectual particle (动态助词; 動態助詞; dòngtài zhùcí): Commonly dubbed aspect markers (動貌標記 or 動貌標誌), the particles signal grammatical aspect. The most renowned ones are the perfective 了(le), durative 著(zhe), durative 在(zaì), and experiential 過(guò).^{[3]: p. 185[6]}

• Modal particle (语气助词; 語氣助詞; yǔqì zhùcí): Often called sentence-final particles (句末助詞), the particles signal linguistic modality. Common ones include 了(le), 呢(ne), 吧(ba), and 嗎(mā/ma).^{[3]: p. 238}

Particles like 的(dè/de) and 了(le) remain disputable since no satisfactory analysis is present.