衰败的英文：
decay

参考例句：

an effete system of education
衰败的教育制度

What caused feudal warfare to decline?
是什么导致了封建制度的战争的衰败？

A dilapidated or unsanitary dwelling.
陋室破旧，衰败或肮脏的住宅

Pride goeth before destruction and an haughty spirit before a fall.
骄傲导向灭亡，傲慢必衰败。

By now the power of the Roman Empire was on the wane
到这时，罗马帝国已日益衰败。

The neighborhood after declining for years, was coming up again.
这周围的地区在多年衰败后，又兴旺发达起来。

History sometimes seems to teach us that all nations decay in the course of time.
历史有时似乎在教导我们，所有的国家最后都会衰败。

The city has gone downhill since the war broke out
自从战争爆发以来，这座城市日益衰败。

The neighborhood after declining for years, was coming up again
这周围的地区在多年衰败后，又兴旺发达起来。

During the middle ages, Greek civilization declined and became effete.
在中世纪期间，希腊文明开始衰落直至衰败。

decay是什么意思：
v. 使腐烂，使腐朽；衰败，衰退，衰落
n. 腐败、衰退的状态

The vegetables have begun to decay.
那些蔬菜已开始腐烂。

To cause to decay and have a foul odor.
使…腐烂导致腐败并发生恶臭

His mental decay is distressing.
他的智力衰退令人苦恼。

The dampness of the climate decayed the books.
气候潮湿，把书都霉坏了。

The fruit decayed in the damp weather.
在潮湿的天气下，水果腐烂了。