Often used as a shorter form of 一週間, especially in compounds or when the context makes the time unit clear. Can function as a noun or adverbially.
See also: 一週間
I try to exercise once a week.
This work won't be finished in one week.
一周 (いっしゅう) means 'one lap/circuit' while 一週 (いっしゅう) — same pronunciation, different kanji — means 'one week'.
one week
Standard kanji spelling; high frequency in news and general use.
Numerical variant, common in schedules, tables, and informal writing.
Compound of 一 (one) and 週 (week). The reading いっしゅう results from the regular sound change of 一 (いち) before an unvoiced consonant.