'副词' (fù cí) literally means 'auxiliary word' — 副 (fù) conveys 'secondary', 'subsidiary', or 'supporting', while 词 (cí) means 'word' or 'term'. Together, they name the grammatical category of words that modify verbs, adjectives, other adverbs, or entire sentences — expressing manner, time, frequency, degree, or certainty. Unlike English, Chinese adverbs often appear before the verb they modify and rarely change form.

In Chinese grammar instruction, 副词 is a foundational term used in textbooks and classrooms to classify words like 很 (hěn, 'very'), 经常 (jīngcháng, 'often'), 立刻 (lìkè, 'immediately'), and 不 (bù, 'not'). Learners encounter it early when studying sentence structure, especially in contrast with nouns, verbs, and adjectives. It's not used conversationally as a standalone lexical item but appears frequently in linguistic explanations and language-learning materials.