‘入伍’ literally means ‘enter the ranks’ — ‘入’ (rù) means ‘to enter’, and ‘伍’ (wǔ) historically refers to a basic military unit of five soldiers, later extended to mean ‘military service’ or ‘armed forces’ as a whole. Together, 入伍 specifically denotes the formal act of enlisting in the military, usually for compulsory or voluntary national service. It is a formal, neutral-to-solemn term used in official contexts, news reports, government notices, and personal narratives about military service.

The word emphasizes the beginning of active duty rather than general interest in the military or preparation (e.g., training or application). It’s commonly used with time markers (e.g., 去年入伍, ‘enlisted last year’) or subjects indicating age, nationality, or status (e.g., 大学生入伍, ‘college students enlisting’). Unlike broader terms like 参军 (cān jūn), 入伍 focuses on the concrete moment of joining and assuming soldier status.