lethargy
词根词缀：
lethal adj. 致命的
leth 遗忘 + al …的 → 最致命的伤害就是被彻底遗忘 → 致命的
lethargic adj. 昏睡的；没精打采的
leth 遗忘 + argic → 昏睡时就忘了一切 → 昏睡的
lethargy n. 昏睡
leth 遗忘 + argy → 睡着了就一切都忘了 → 昏睡
数据来源：新东方英语词汇速记大全
相关例句：
The onset is usually gradual and associated with anorexia, lethargy.
通常起病渐进，伴有厌食，昏睡。
Several hours after the surgery, she was still in her lethargy.
手术过后几小时，她仍然昏睡不醒。
Has a deep, we do not know why can not even sleep, forgetting lethargy.
也深了，不知道为什么无法入眠，忘记了困倦。
There is lethargy, heaviness, inertia every where in the nature.
自然界里充满了昏沉慵懒，沉重，惰性的能量。
Symptoms usually begin with a high fever, lethargy, depression, and loss of appetite.
通常开始的时候伴有发烧，昏睡，忧郁和食量下降。
Chytridiomycosis causes lethargy and convulsions, and thickens the skin that frogs breathe through.
壶菌病会引起嗜睡和惊厥，并使得青蛙呼吸通道皮肤增厚。