The Chinese word 骨髓 (gǔsuǐ) is a compound term formed by combining two characters: 骨 (gǔ), meaning "bone", and 髓 (suǐ), meaning "marrow" or "pith". It is a logical, descriptive formation where the first character specifies the location (bone) and the second specifies the essential substance within it (marrow), directly creating the literal meaning "bone marrow". This follows a common modifier-head structure in Chinese, similar to "railroad" in English. Figuratively, the term extends to signify the innermost essence, core, or spirit of something, as marrow is seen as the vital center of the bone, demonstrating how Chinese often forms abstract concepts from concrete, physical compounds.