ちょっと一杯[chottoippai] let's have a quick drink
ばつ一[batsuichi] being once divorced
一向[hitaburu] nothing but
サラダ一皿[saradahitosara] plate of salad

安全第一[anzendaiichi] safety first
一か八か[ichikabachika] sink or swim
一っ走り[hitoppashiri] spin (as in 'take a car for a spin')
一つ一つ[hitotsuhitotsu] one-by-one

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

九寸五分[kusungobu] dagger
弦楽五重奏曲[gengakugojuusoukyoku] string quintet
五つ[itsutsu] five
五つ子[itsutsugo] quintuplets
五悪[goaku] the five sins in Buddhism (murder, theft, adultery, falsehood and drink)

五音々階[goononkai] pentatonic scale
五戒[gokai] the five precepts (prohibitions against killing, theft, sexual misconduct, lying and intemperance)
五官[gokan] the five sense organs
五感[gokan] the five senses

沃度丁幾[youdochinki] tincture of iodine
豊沃[houyoku] fertility
沃素[youso] iodine (I)
肥沃[hiyoku] fertility
沃土[yokudo] rich soil

沃地[yokuchi] fertile land
沃野[yokuya] fertile fields or plain
沃化[youka] iodization
沃野千里[yokuyasenri] vast expansion of fertile land
沃度[youdo] iodine

バイオ素子[baiososhi] bio-device
弗素[fusso] fluorine (F)
一酸化炭素[issankatanso] carbon monoxide
栄養素[eiyouso] nutrient
塩化水素[enkasuiso] hydrogen chloride

塩素[enso] chlorine (Cl)
塩素酸[ensosan] chloric acid
塩素酸塩[ensosanen] chlorate
音楽の素質[ongakunososhitsu] aptitude for music
音素[onso] phoneme