週期 is read as しゅうき (shuuki) and means cycle.
しゅうき
shuuki
しゅうまつ
weekend
しゅうない
by the end of this week
しゅういっかい
once per week
しゅうさんかい
three times a week
しゅうかんてんきよほう
weather forecast for coming week
しゅうきゅうふつかせい
system of having two days off in at least one week each month
しゅうきゅうみっかせい
four-day workweek system
しゅうじ
weekly
しゅうまつきぎょう
running a start-up company after work or on weekends
しゅうほう
weekly report
しゅうばん
weekly duty
しゅうきゅうせい
six-day workweek system