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

コスト効率[kosutokouritsu] cost effectiveness
圧縮率[asshukuritsu] compressibility
引率[insotsu] leading
円周率[enshuuritsu] Pi (3.1415926..)
黄金率[ougonritsu] golden mean

拡大率[kakudairitsu] rate of magnification
確率[kakuritsu] probability
確率モデル[kakuritsumoderu] stochastic model
確率過程[kakuritsukatei] stochastic process
確率誤差[kakuritsugosa] random error