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

변경change; alteration 변동change; fluctuation 변화change 가변variability 가변성variability; changeability 가변적being variable 가변적changeable; changing; variable 개변change; reformation; renovation 격변sudden change; rapid change; violent upheaval; cataclysm 격변기period of upheaval