The kanji 髄 primarily conveys the meaning of "marrow" or "pith." This refers to the soft, central part of bones, or in a broader sense, the essence or core of something. It can relate to the vital part of the body, or even the essential element of an idea or concept.

・On-yomi (音読み): ズイ (zui) ・Kun-yomi (訓読み): None, but it is often used in compound words.

⚫︎骨髄 Translation: Bone marrow ⚫︎脊髄 Translation: Spinal cord ⚫︎真髄 Translation: Essence; quintessence

The kanji 髄 is a 形声文字 (keisei moji), or phono-semantic compound. It is composed of two parts: the radical 骨 (hone), meaning "bone," and the phonetic component ユイ. The 骨 radical indicates the character’s relation to bones, while the phonetic component ユイ provides a sound clue for the reading. This structure points directly to the core meaning of “marrow” or the inner substance related to bones.