衰败用英语怎么说

wane [wein]
n. 衰微,亏缺,变弱
v. 变小,亏缺,呈下弦
例句:
The empire was on the wane after its period of prosperity.
帝国经过全盛以后逐渐衰落。
The moon waxes and wanes every month.
月亮每个月都有盈亏。
By now the power of the Roman Empire was on the wane.
到这时，罗马帝国已日益衰败。