wax and wane
盈虧變化，波動不定
書面或口語·描述波動或循環
英文釋義
to go through cycles of increase and decrease, rise and fall; to fluctuate in intensity or popularity
例句
The popularity of that singer has waxed and waned over the years.
典故來源
源自月亮的盈虧現象，比喻事物周期性的增減或變化。