an event that occurs when something passes from one state or phase to another

move or sway in a rising and falling or wavelike pattern

a variation in circumstances or fortune at different times in your life or in the development of something

(chemistry) variability in chemical composition without variation in crystalline form

a variation that deviates from the standard or norm

an event in which one thing is substituted for another

recurring fluctuations in economic activity consisting of recession and recovery and growth and decline