サンプリング周波数[sanpuringushuuhasuu] sampling frequency
一周忌[isshuuki] first anniversary of death
一周期[isshuuki] period (in astronomy)
一周年[isshuunen] one full year
円周[enshuu] circumference

円周率[enshuuritsu] Pi (3.1415926..)
外周[gaishuu] outer circumference
基本周波数[kihonshuuhasuu] fundamental frequency
月経周期[gekkeishuuki] menstrual cycle
周章てる[awateru] to become confused (disconcerted, disorganized, disorganised)