It belongs to a phonetic family with 住, 注, 駐, and 柱 — they share the 主 component and the reading チュウ.
A common word using 主 is ご主人 (ごしゅじん), meaning “(your, her) husband”.
Don't confuse it with 王 and 玉 — 玉 (jewel) is 王 with a dot; 主 (master) has a dot on top