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

一念発起[ichinenhokki] being resolved to (do something)
引き起す[hikiokosu] to cause
縁起[engi] omen
喚起[kanki] arousal
起きる[okiru] to get up

起上る[okiagaru] to rise
起す[okosu] to raise
起こり得る[okoriuru] to be possible to occur
起る[okoru] to occur
起つ[tatsu] to rise up