‘骨干’ (gǔ gàn) literally combines ‘bone’ (骨) and ‘trunk’ or ‘main stem’ (干), evoking the image of the central supporting structure—like the spine in a living body. Figuratively, it refers to a person who serves as the core, essential, or most reliable member of a group, team, organization, or movement. It emphasizes both structural importance and functional indispensability—not just seniority or title, but active, foundational contribution.

This term is commonly used in organizational, professional, and social contexts: for example, describing experienced teachers in a school, veteran engineers in a tech firm, or long-standing volunteers in a community initiative. While it can occasionally refer to literal bone structure in biological or medical discussions (especially in compound terms like 骨干细胞), its dominant modern usage is metaphorical and human-centered. It carries positive connotations of strength, stability, and quiet leadership.