一も二も無く[ichimonimonaku] unhesitatingly
一言二言[hitokotofutakoto] a word or two
一石二鳥[issekinichou] killing two birds with one stone
一二に及ばず[ichininioyobazu] right away
一姫二太郎[ichihimenitarou] It's good to have a girl first and then a boy

うり二つ[urifutatsu] as alike as two melons (two peas in a pod)
黄道十二宮[koudoujuunikyuu] twelve signs of the zodiac
二度[futatabi] again
最小二乗法[saishounijouhou] least-squares method
三十二分音符[sanjuunibuonpu] 32nd note

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

渋柿[shibugaki] astringent persimmon
熟柿[jukushi] ripe persimmon
樽柿[tarugaki] persimmons mellowed in a sake cask
熟柿主義[jukushishugi] laying low, awaiting one's chance
熟柿臭い[jukushikusai] smelling of (stale) liquor

柿色[kakiiro] reddish-brown
柿渋[kakishibu] (astringent) persimmon juice
柿落し[kokeraotoshi] opening of a new theater (theatre)
吊し柿[tsurushigaki] persimmon (hung to dry)

アセンブリー言葉[asenburiikotoba] assembly language
一葉[ichiyou] one leaf
右葉[uyou] right lobe
押し葉[oshiba] pressed leaves
観葉植物[kanyoushokubutsu] decorative plant

棄言葉[sutekotoba] sharp parting remark
京葉[keiyou] Tokyo and Chiba
言葉[kotoba] language
言葉づかい[kotobazukai] speech
口言葉[kuchikotoba] spoken language