(a numeral noun/adjective)+째 means "(a numeral)th" e.g. 첫째 = first 다섯째 = fifth 사흘째 = third day (a period noun) + 째 means "for (a period noun)" e.g. 석 달째 = for 3 months 일주일째 = for a week 아빠가 일주일째 집에 안 들어와 My father has not come home for a week until now. My father has stayed out for a week until now.