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

介殻[kaikaku] sea shell
灰殻[haigara] ashes
貝殻[kaigara] shell
そば殻[sobagara] buckwheat chaff
甲殻[koukaku] carapace

甲殻類[koukakurui] crustacean
菜種殻[natanegara] rapeseed hulls
出し殻[dashigara] grounds (of tea and coffee)
出殻[degara] grounds (of tea and coffee)

異類[irui] varieties
一類[ichirui] same kind
円虫類[enchuurui] round worms
塩類[enrui] salts
塩類溶液[enruiyoueki] saline

貝類[kairui] shellfish
柑橘類[kankitsurui] citrus fruits
希土類[kidorui] rare earth
魚貝類[gyokairui] marine products
魚類[gyorui] fish