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

その反面[sonohanmen] on the other hand
に反して[nihanshite] against
違反者[ihansha] violator (of a law)
違反[ihan] violation (of law)
一律減反[ichiritsugentan] reduction in area of rice under cultivation

陰性反応[inseihannou] negative reaction (in patient)
化学反応[kagakuhannou] chemical reaction
可逆反応[kagyakuhannou] reversible reaction
核反応[kakuhannou] nuclear reaction
核反応炉[kakuhannouro] nuclear reactor