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

井の中の蛙大海を知らず[inonakanokawazutaikaiwoshirazu] parochial
井桁[igeta] well lining
井戸[ido] water well
井戸屋形[idoyakata] well roof
井戸掘り[idohori] well digging

井戸綱[idozuna] well rope
井戸車[idoguruma] well pulley
井戸水[idomizu] well water
井戸側[idogawa] well curb
井戸替え[idogae] well cleaning

井の中の蛙大海を知らず[inonakanokawazutaikaiwoshirazu] parochial
雨蛙[amagaeru] tree frog (esp. the Japanese tree frog, Hyla japonica)
蛙の子は蛙[kaerunokohakaeru] like father, like son
蛙跳び[kaerutobi] (game of) leapfrog
殿様蛙[tonosamagaeru] black-spotted pond frog (Rana nigromaculata)

蟇蛙[hikigaeru] toad (esp. the Japanese toad, Bufo japonicus)
蛙又[kaerumata] curved wooden support on top of the main beam of a house, now mainly decorative (shape evocates an open-legged frog)
青蛙[aogaeru] green (tree) frog
赤蛙[akagaeru] any brown or reddish-brown frog (esp. of family Ranidae)