逸速く[ichihayaku] promptly
音速[onsoku] speed of sound
加速[kasoku] acceleration
加速運動[kasokuundou] accelerated motion
加速度[kasokudo] acceleration

快速[kaisoku] high speed
快速電車[kaisokudensha] high-speed train
角速度[kakusokudo] angular velocity
急速[kyuusoku] rapid (e.g. progress)
減速[gensoku] deceleration

悪達者[warudassha] fast slipshod work
伊達[date] elegance
伊達姿[datesugata] flashy appearance
伊達者[datesha] dandy
伊達衆[dateshuu] dandy

伊達女[dateonna] flapper
伊達男[dateotoko] dandy
伊達着[dategi] showy clothes
栄達[eitatsu] fame
下達[katatsu] commanding a subordinate