座
zuò · HSK 2
seat
💺 广 (shelter) + two 人 + 土 (earth) — people sitting on ground under a roof = a seat
Original sense: a place to sit. Extended to base/stand (what holds something up) and to constellation (a seat in the sky). Measure word for large fixed things: 一座山 one mountain, 一座桥 one bridge.
座 — 广 (shelter) + 坐 (to sit)
Originally written as 坐, meaning 'to sit' (two people 人人 sitting on the ground 土). The shelter radical 广 was added to specify the place where one sits — a seat, throne, or platform. 坐 remained the verb 'to sit,' while 座 became the noun 'seat.'