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

安全第一[anzendaiichi] safety first
及第[kyuudai] passing an examination
及第者[kyuudaisha] successful examinee
及第点[kyuudaiten] passing mark
次第[shidai] dependent upon

次第に[shidaini] gradually (progress into a state)
次第書き[shidaigaki] printed program
式次第[shikishidai] program of a ceremony (programme)
手当たり次第[teatarishidai] using anything one can lay one's hands on
出来次第[dekishidai] as soon as completed

胃液[ieki] gastric juice
胃炎[ien] gastritis
胃下垂[ikasui] gastroptosis
胃癌[igan] stomach cancer
胃鏡[ikyou] gastroscope

胃散[isan] stomach medicine
胃酸[isan] stomach acid
胃弱[ijaku] dyspepsia
胃洗浄[isenjou] stomach pumping