'证书' (zhèng shū) literally combines '证' (zhèng), meaning 'evidence' or 'proof', and '书' (shū), meaning 'book' or 'document'. Together, they form a compound noun meaning 'certificate' — an official document that formally attests to a fact, achievement, qualification, or status. Certificates are commonly issued by schools, government agencies, professional bodies, or testing organizations.

This word is used in formal and administrative contexts — for example, graduation certificates, vaccination certificates, language proficiency certificates (like HSK), or professional licenses. It is always a countable noun and typically appears with measure words like '一(张)' (yì zhāng) for paper-based certificates or '一(本)' (yì běn) for booklet-style ones. Unlike the more general '证明' (zhèngmíng), which refers to any kind of verification statement, '证书' specifically denotes a standardized, often embossed or officially signed document.