御中[onaka] stomach
御話中[ohanashichuu] busy (phone)
アル中[aruchuu] alcoholism
π中間子[paichuukanshi] pi meson
暗中[anchuu] in the dark

暗中摸索[anchuumosaku] groping in the dark
意中[ichuu] one's mind
意中の女[ichuunoonna] sweetheart
井の中の蛙大海を知らず[inonakanokawazutaikaiwoshirazu] parochial
一日中[ichinichijuu] all day long

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

イ長調[ichouchou] A major
データビット長[deetabittochou] data bit length
ト長調[tochouchou] G major
ニ長調[nichouchou] D major
ハ長調[hachouchou] C major

ヘ長調[hechouchou] F major
ホ長調[hochouchou] E major
ロ長調[rochouchou] B major
委員長[iinchou] committee chairman
意味深長[imishinchou] with profound (often hidden) meaning