infirmity
n. 虚弱
On leaving the hospital, the patient felt almost too weak to walk, but he soon overcame this infirmity.
离开医院时，病人觉得虚弱得几乎走不动，但他很快就克服了虚弱。
debilitate
vt. 使虚弱　 反：invigorate　增添活力，使精力充沛
The patient had been so debilitated by the fever that he lacked the strength to sit up.
这病人因发烧而一直很虚弱，以致于连坐起来的力气都没有。
enervate
vt. 使无力
Enervated by the heat, we rested under a shady tree until our strength was restored.
热得没力时我们坐在一棵阴凉的树下休息，直到力气恢复为止。
incapacitate
vt. 使不能
Ruth will be absent today. She is incapacitated by a sore throat.
露丝令天将缺席，喉咙痛使她不能出席。
decadent
adj. 衰微的　反：flourishing　繁荣的
When industry moves away, a flourishing town may quickly become decadent.
工业移走时，一个繁荣的城镇很快就会衰徽。
decrepit
adj. 老朽的　 反：sturdy　强健的
Bill rode past the street on a horse that looked decrepit and about to collapse.
比利骑一匹看起来既老朽又快倒了的马经过街上。
dilapidated
adj. 荒废的
Up the road was an abandoned farmhouse, partially in ruins, and near it a barn, even more dilapidated.
沿那条路走下去，有一间部分毁坏的废弃农舍，农舍附近有一个谷仓，荒废得更厉害。
flimsy
adj. 薄弱的
Judy understands algebra well but I have only a flimsy grasp of the subject.
朱蒂精通代数，但我对这科的理解却很薄弱。
frail
adj. 虚弱的　　反：robust 强健的
To be an astronaut, you must be in robust health. It is not an occupation for a frail person.
做太空人必须身体强壮，虚弱的人不适合进这行业。