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

収繭[shuuken] cocoon crop
二つ繭[futatsumayu] double cocoon
繭を掛ける[mayuwokakeru] to spin a cocoon
繭価[mayuka] price of a cocoon
繭玉[mayudama] New Year's decoration with cocoon-shaped cakes

繭紬[kenchuu] pongee (unbleached silk)
繭糸[kinuito] silk thread
春繭[harumayu] spring cocoon crop
山繭蛾[yamamayuga] Japanese oak silkmoth (Antheraea yamamai)