座位 (zuòwèi) is the everyday noun for a physical seat (chair, bench, train seat). It's more concrete than 位置 (wèizhì 'position/place'), which can refer to any location, not just a seat. 座 (zuò) as a noun is shorter and often used in compounds or as a classifier, not alone for a specific seat. 位子 (wèizi) is a colloquial synonym for a specific spot (e.g., at a table), but 座位 is the standard, neutral word.