柱 is built from the 木 and 主 components.
It belongs to a phonetic family with 住, 注, and 駐 — they share the 主 component and the reading チュウ.
A common word using 柱 is 電柱 (でんちゅう), meaning “telephone pole, telegraph pole, light pole”.
Don't confuse it with 住, 往, 注, and 駐.
