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

伸べる[noberu] to lay out (a futon)
延伸[enshin] extension
屈伸[kusshin] elasticity
欠伸[akubi] yawn
差伸べる[sashinoberu] to hold out

三伸[sanshin] second postscript
伸し[noshi] stretching
伸し掛る[noshikakaru] to lean on
伸し上がる[noshiagaru] to stand on tiptoe
伸し上げる[noshiageru] to promote