급감rapid decrease; sharp fall; nosedive 급증rapid increase 급행열차express train 긴급emergency 긴급회의emergency meeting 응급실ER; emergency room 초특급being very speedy 특급special express 화급urgency; emergency 구급relief; rescue

유행outbreak 한류Korean wave 교류mixture of currents; intersection of streams 대유행being widely popular; fad; craze 상류upper region 유통circulation; ventilation 유행병epidemic 유행어fad word; buzzword; in-word 청산유수fluent speech 초일류tiptop; summit