周 (zhōu) means 'week' — it's used like 星期 (xīngqī) but is slightly more formal and common in written schedules (e.g., 本周 'this week'). As a classifier, 周 counts laps or circuits (跑三周 'run three laps'), while 遍 counts full repetitions of an action (看一遍 'watch once').