懐旧[kaikyuu] recalling the old days
旧ソ連[kyuusoren] former Soviet Union
旧悪[kyuuaku] past misdeeds
旧衣[kyuui] worn-out clothes
旧詠[kyuuei] ancient poems

旧怨[kyuuen] old grudge
旧縁[kyuuen] old relationship
旧恩[kyuuon] old favors
旧仮名遣[kyuukanazukai] former (i.e. before the post-WWII reforms) kana usage in writing the readings of kanji

ヨガの流行[yoganoryuukou] the cult of yoga
亜流[aryuu] bad second
暗流[anryuu] undercurrent
一次電流[ichijidenryuu] primary current
一流[ichiryuu] first-class

溢流[itsuryuu] overflow
渦流[karyuu] swirling current
押流す[oshinagasu] to wash away
横流し[yokonagashi] diversion into illegal channels
横流れ[yokonagare] flowing into the black market