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

改善[kaizen] betterment
勧善懲悪[kanzenchouaku] rewarding good and punishing evil
勧善懲悪劇[kanzenchouakugeki] morality play
偽善[gizen] hypocrisy
偽善者[gizensha] hypocrite

最善[saizen] the very best
慈善[jizen] charity
慈善家[jizenka] charitable person
慈善会[jizenkai] philanthropic society
慈善市[jizenichi] charity bazaar

と仮定して[tokateishite] assuming that ...
と仮定しても[tokateishitemo] even assuming that ...
プリンター設定[purintaasettei] printer setup
モデムの設定[modemunosettei] modem setup
安定[antei] stability

安定化[anteika] stabilization
安定器[anteiki] stabilizer
安定性[anteisei] stability
安定同位体[anteidouitai] stable isotope
案の定[annojou] just as one thought

威張り散らす[ibarichirasu] to domineer
胃散[isan] stomach medicine
逸散に[issanni] at top speed
一目散[ichimokusan] at full speed
一目散に[ichimokusanni] at full speed

雲散霧消[unsanmushou] vanishing like mist
解散[kaisan] breakup
拡散[kakusan] scattering
閑散[kansan] deserted (esp. store, market, town, streets)
言散らす[iichirasu] to spread (a report)