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

１枚[ichimai] one thin flat object
一枚下[ichimaishita] one step lower
一枚貝[ichimaigai] univalve
一枚看板[ichimaikanban] (a) leading player
一枚岩[ichimaiiwa] monolith

一枚上[ichimaiue] one step higher
何枚[nanmai] how many thin flat objects?
３枚[sanmai] three flat objects (e.g. tickets, pieces of cloth, etc.)
三枚目[sanmaime] comedian
紙一枚[kamiichimai] one sheet of paper

ギックリ腰[gikkurigoshi] strained back
丸腰[marugoshi] unarmed
及び腰[oyobigoshi] bent back
けんか腰[kenkagoshi] belligerent
腰掛る[koshikakeru] to sit (down)

腰を下す[koshiwoorosu] to sit down
腰かけ[koshikake] seat
腰巻[koshimaki] loincloth
腰元[koshimoto] chamber maid