1A period measured in units of seven days; usually combined with a number, as in 'three weeks' (三週間) or 'two weeks' (二週間).
三週間前に出張から戻りました。
I returned from a business trip three weeks ago.
病気で二週間学校を休んだ。
I missed school for two weeks because of illness.
その工事は約一週間かかる見込みです。
The construction is expected to take about one week.