1.
one week
A period of seven days.
一週間休んだ。
I took a week off.
一週間に一回運動する。
I exercise once a week.
結果が出るまで一週間ぐらいかかります。
It takes about a week for the results to come out.
一週間 is the standard way to say "one week" as a duration. Note the sound change (促音便): いち + しゅうかん → いっしゅうかん.
COUNTING WEEKS:
- 一週間 (1 week), 二週間 (2 weeks), 三週間 (3 weeks)
- 何週間: how many weeks?
COMMON PATTERNS:
- 一週間に一度/一回: once a week
- 一週間前: a week ago
- 一週間後: a week later
- 一週間ぐらい: about a week
CONTRAST:
- 一週間: one week (duration)
- 一週: one lap/circuit (different meaning)