A zìdiǎn is a reference book or digital tool that lists Chinese characters (and often words) in systematic order—typically by pinyin, radical, or stroke count—with definitions, pronunciations, parts of speech, and example usages. The character zì means 'character' or 'written symbol', while diǎn means 'classic', 'canon', or 'authoritative reference'—together they convey the idea of an authoritative collection of written characters.

This word is used broadly for both monolingual dictionaries (e.g., Xiàndài Hànyǔ Cídiǎn) and bilingual ones (e.g., Hàn-Yīng Zìdiǎn). It’s commonly encountered in academic, learning, and everyday contexts—students consult it during study, writers verify usage, and learners rely on it to expand vocabulary. While modern usage includes apps and online tools, the term zìdiǎn still carries its traditional meaning and remains unambiguous in spoken and written Mandarin.