noun
Botanical term for the soft central tissue in plant stems.
植物の茎の髄は水分や養分を蓄える。
The pith of a plant stem stores water and nutrients.
noun
Anatomical term for bone marrow; also used in compounds like 脊髄 (spinal cord).
骨髄移植には適合するドナーが必要だ。
A matching donor is needed for a bone marrow transplant.
Specifically bone marrow; 髄 alone is a broader term that can refer to pith or marrow.
Spinal cord; a compound using 髄, not a standalone synonym.
The kanji 髄 is composed of 骨 (bone) and a phonetic component, originally referring to marrow. The reading ずい is the on'yomi.