also: じ
noun, noun, used as a suffix
Refers to the movable bridge of a koto or similar stringed instrument; also used as a suffix in compound terms like 琴柱 (ことじ).
琴の柱を動かして調弦する。
I tune the koto by moving its bridges.
この柱は象牙でできている。
This bridge is made of ivory.
noun, noun, used as a suffix
Only with reading ちゅう
Used in geometry and technical contexts; reading is always ちゅう. Often appears as a suffix in words like 円柱 (cylinder) and 角柱 (prism).
円柱の体積を計算する。
Calculate the volume of the cylinder.
三角柱は五つの面を持つ。
A triangular prism has five faces.
The kanji 柱 originally means 'pillar' or 'post'. Its use for a koto bridge likely comes from the visual similarity of the small standing pieces to pillars. The geometric sense is a later extension, probably from the idea of a solid standing shape.