在职 (zài zhí) literally means 'at duty' or 'in post', combining 在 (zài, 'at' or 'present') and 职 (zhí, 'duty', 'office', or 'position'). It functions primarily as an adjective describing someone who is currently holding a job or serving in an official capacity — not retired, unemployed, or on leave. It emphasizes active, ongoing employment status and is commonly used in formal, administrative, or institutional contexts, such as HR documents, educational programs for working adults, or official statistics.

The term often appears in compound phrases like 在职人员 (zài zhí rényuán, 'employed personnel'), 在职培训 (zài zhí péixùn, 'on-the-job training'), or 在职研究生 (zài zhí yánjiūshēng, 'part-time graduate student'). Unlike colloquial terms like 上班 (shàngbān, 'to go to work'), 在职 carries a neutral-to-formal register and focuses on status rather than activity. It’s rarely used to describe students, retirees, or freelancers unless they hold an official position within an organization.