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

何の位[donogurai] how long
リーダーシップ的地位[riidaashipputekichii] leadership position
安定同位体[anteidouitai] stable isotope
位階[ikai] court rank
位階勲等[ikaikuntou] court rank and honors

位冠[ikan] ancient headgear showing rank
位官[ikan] rank and official position
位記[iki] court rank diploma
位記追贈[ikitsuisou] conferment of posthumous rank