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

ジェット推進研究所[jettosuishinkenkyuusho] Jet Propulsion Laboratory
一進一退[isshinittai] now advancing and now retreating
一歩前進[ippozenshin] (a) step forward
栄進[eishin] promotion
詠進[eishin] presentation of poem (to court)

仮進級[karishinkyuu] conditional promotion
勘進[kanshin] reporting after careful investigation
勧進[kanjin] temple solicitation
勧進元[kanjinmoto] backer
勧進帳[kanjinchou] temple solicitation book