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

下瞼[shitamabuta] lower eyelid
上瞼[uwamabuta] upper eyelid
眼瞼[ganken] eyelid
挟瞼器[kyoukenki] entropion forceps
一重瞼[hitoemabuta] single-edged eyelid

二重瞼[futaemabuta] double-edged eyelid
開瞼器[kaikenki] eyelid speculum
眼瞼閉鎖反射[gankenheisahansha] blink reflex
眼瞼下垂[gankenkasui] ptosis

意味深重[imishinchou] with profound (often hidden) meaning
一重ね[hitokasane] suit
一重継ぎ[hitoetsugi] sheep bend (knot)
一重桜[hitoezakura] cherry tree bearing single blossoms
荷重[kajuu] load

過重[kajuu] overweight
気が重い[kigaomoi] depressed
貴重[kichou] precious
貴重品[kichouhin] valuables
起重機[kijuuki] crane