安全期[anzenki] safe period
暗黒期[ankokuki] eclipse period
一期[ichigo] one's life time
一期[ikki] one term
一期一会[ichigoichie] once-in-a-lifetime encounter (hence should be cherished as such)

一周期[isshuuki] period (in astronomy)
一定期間[itteikikan] fixed interval
延期[enki] postponement
延期になる[enkininaru] to be postponed
沖積期[chuusekiki] alluvial period

マルコフ遷移[marukofuseni] Markov transition
移す[utsusu] to change
移り気[utsurigi] whim
移りゆく[utsuriyuku] to change
移り香[utsuriga] lingering scent

移り変り[utsurikawari] change (e.g. season)
移る[utsuru] to move (house)
移ろう[utsurou] to change (with the passage of time)
移管[ikan] transfer of control
移行[ikou] switching over to

行けない[ikenai] wrong
行る[yaru] to send
オリエント急行[orientokyuukou] Orient express
カ行[kagyou] classification for Japanese verb with the dictionary form ending in "ku"
ガ行[gagyou] classification for Japanese verb with the dictionary form ending in "gu"

サ行[sagyou] classification for Japanese verb with the dictionary form ending in "su"
ザ行[zagyou] classification for Japanese verb with the dictionary form ending in "zu"
スパイ行為[supaikoui] espionage
タ行[tagyou] classification for Japanese verb with the dictionary form ending in "tsu"
ダ行[dagyou] classification for Japanese verb with the dictionary form ending in "dzu"