一元[ichigen] unitary
一元化[ichigenka] unification
一元的[ichigenteki] monistic
一元論[ichigenron] monism
一次元[ichijigen] one dimensional

一新紀元[isshinkigen] new era
隠元[ingen] beans
隠元豆[ingenmame] common bean (Phaseolus vulgaris)
家元[iemoto] head of a school (of music, dance)
火の元[hinomoto] origin of fire

これと同じ[koretoonaji] the same as this
と同じ様に[toonajiyouni] in the same way as
安定同位体[anteidouitai] stable isotope
異句同音[ikudouon] in concert
異口同音に[ikudouonni] in one voice

異同[idou] difference
一口同音[ikkudouon] reading in unison
一視同仁[isshidoujin] loving every human being with impartiality
一心同体[isshindoutai] being one in body and soul
一同[ichidou] all present

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