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)

其の後[sonoato] after that
已後[igo] after this
一死後[isshigo] after one out (in Baseball)
気後れ[kiokure] nervous
紀元後[kigengo] post-era

空前絶後[kuuzenzetsugo] (so marvelous or horrible that it may be) the first and probably the last
兄後[anigo] elder brother
月後れ[tsukiokure] a month or older
午後[gogo] afternoon
午後中[gogojuu] throughout the afternoon