Cycle, Period
noun
If you follow the circumference of a period of time, you end up back at the beginning and it makes a full cycle. Events in history always repeat, right?
しゅうき
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
私の生理周期はいつも大体２８日です。
My menstrual cycle is usually about twenty-eight days.
人の人生って、山あり谷ありが１２年周期で回っているらしいよ。
It seems that people's lives revolve through ups and downs in cycles of about 12 years.
東北の天気は短い周期で変わる。
Tohoku’s weather changes in short cycles.