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

異句同音[ikudouon] in concert
一句[ikku] phrase (verse, line)
一句詠む[ikkuyomu] to make up a haiku poem
引用句[inyouku] quotation
下の句[shimonoku] the last part of a poem or Bible verse

下句[geku] the last part of a poem or Bible verse
佳句[kaku] beautiful passage of literature
慣用句[kanyouku] idiomatic usage
慣用語句[kanyougoku] idiom
脅し文句[odoshimonku] threatening words