This is the 739th most frequent Korean word.
일주일
One week.
Here, 일주일 (il-ju-il) means 'a week' as a duration of time (for a week).
나는 일주일 동안 한국에 머물렀습니다.
I stayed in Korea for a week.
In this sentence, 일주일 (il-ju-il) refers to 'a week' as a specific point in time (in a week).
일주일 후에 다시 만납시다.
Let's meet again in a week.
Here, 일주일 (il-ju-il) is used to refer to a previous time frame of one week.