双節棍[nunchaku] nunchaku (two linked fighting sticks)
一双[issou] pair (esp. of folding screens)
一卵性双生児[ichiranseisouseiji] identical twins
双紙[soushi] written work (esp. a bound text, as opposed to a scroll)
自己双対[jikosoutsui] self dual

双刃[moroha] double-edged
双暗車[souansha] twin propellers
双殻類[soukakurui] bivalves
双眼[sougan] both eyes

暗い[kurai] dark
暗がり[kuragari] darkness
暗に[anni] implicitly
暗やみ[kurayami] darkness
暗うつ[anutsu] gloom

暗雲[anun] dark clouds
暗褐色[ankasshoku] dark brown
暗きょ[ankyo] subterranean drain
暗君[ankun] foolish ruler
暗号[angou] code

グリーン車[guriinsha] green car (1st class)
愛車[aisha] (one's) beloved car
医療車[iryousha] clinic car
井戸車[idoguruma] well pulley
１等車[ittousha] first-class carriage (coach)

一輪車[ichirinsha] unicycle
横車[yokoguruma] perverseness
下り列車[kudariressha] trains going away from the capital
下車[gesha] alighting (from train, bus, etc.)
火の車[hinokuruma] fiery chariot (which carries the souls of sinners into hell)