衰退的英文：
decline
fall
decline
drop
decay
falter

参考例句：

Idleness rusts the mind. ——Aesop
懒惰使头脑衰退。——伊索

Premature ovarian failure
卵巢功能早期衰退

plans to revitalize inner - city neighborhoods;tried to revitalize a flagging economy.
计划给内城邻里关系以新气象;试图给正在衰退的经济以新生

As people grow old, they will decay mentally as well as physically.
人们年老时脑力和体力都会衰退。

This decline in vigour with the passing of time is called ageing.
这种随着时间流逝的活力衰退就叫做衰老。

His hearing has started to go.
他的听力开始衰退。

To undergo degeneration.
经历退化、衰退、堕落.

To fall away or back;decline or recede.
回落跌落;衰退或消减

His sight is beginning to fail.
他的视力开始衰退。

Lose ground; fall behind
撤退;失势;衰退

decline是什么意思：
n. 下降；减少，衰退，衰落，最后部分；晚年，倾斜
v. 下降，下跌；减少；倾斜；婉拒；使降低，使变格

sink into a decline
开始衰落，衰弱下去，体力衰退

The population is on the decline.
人口在减少。

The decline of literature indicates the decline of a nation.
文学的衰落表明一个民族的衰落。

fall是什么意思：
v. 落下；倒塌；摔倒；下降；减弱；阵亡
n. 摔倒；下降；秋天；垮台；陷落；瀑布
adj. 秋天的

Sleet is falling.
天上下起了冰雹。

fall into disfavour
失宠失众望

We observed the barometer fall. [The barometer was observed to fall.]
我们看见晴雨表下降。

drop是什么意思：
v. 落下；降低；垂下；停止；终止；放弃；与…断绝联系
n. 落差；球状糖果；珠，滴；少量

A small amount of liquid;a drop.
少量液体；一滴

low-velocity drop
低速度空投

high velocity drop
高速度空投