词汇 (cí huì) means 'vocabulary' — the total set of words a person knows or uses in a language. The first character 词 (cí) means 'word' or 'term', while 汇 (huì) means 'to gather' or 'to collect'. Together, they literally convey the idea of 'a collection of words'. This word is used formally and academically — you’ll see it in textbooks, language learning contexts, and discussions about language proficiency.

Unlike the more casual term 单词 (dān cí), which refers to individual 'words', 词汇 emphasizes the collective, systemic nature of word knowledge — for example, 'advanced vocabulary' or 'vocabulary size'. It’s commonly paired with measure words like 量 (liàng) or adjectives like 丰富 (fēngfù, 'rich') or 扩大 (kuòdà, 'to expand'). It’s not used for counting single items (e.g., you wouldn’t say *'three 词汇'*), but rather for describing breadth, range, or development of lexical knowledge.