‘诊断’ (zhěn duàn) is a compound noun meaning ‘diagnosis’ — the process of identifying a disease or condition based on symptoms, tests, and medical examination. The first character, 诊 (zhěn), means ‘to examine (a patient)’ and originally referred to pulse-taking in traditional Chinese medicine; the second, 断 (duàn), means ‘to judge’ or ‘to determine’. Together, they convey the idea of ‘examining and determining’ — precisely what doctors do when reaching a clinical conclusion.

This term is used almost exclusively in formal, professional, or medical contexts — in hospitals, clinics, health reports, or discussions about illness. It’s not used for casual guesses about someone’s well-being (e.g., you wouldn’t say ‘我诊断他累了’). While it can appear in both Western and traditional Chinese medicine settings, it always implies an authoritative, evidence-informed judgment rather than speculation.