sleepy: applies to whatever seems about to fall asleep or to whatever leads to such a state: a ~ little town.


drowsy: carries a stronger implication of the heaviness or languor associated with sleepiness than of an actual need for sleep: grew ~ in the stuffy room.   (languor慵懒懒洋洋不愿动，例如让人困倦的天气疾病，或让人放松的生活爱情suggests inertia induced by an enervating climate or illness or soft living or love，如languor induced by a tropical vacation热带度假使人慵懒）


somnolent: is likely to suggest the sluggishness or inertness accompanying sleepiness more than the actual impulse to sleep: the ~ air of a tropical noon.  (slug缓步虫蛞蝓, 像没有壳的蜗牛的软体动物，行动十分缓慢is a small soft creature, like a snail without a shell, that moves very slowly and often eats garden plants, 如sluggish traffic/economy/black waters/body缓缓移动的车流/经济停滞/缓慢流动的河水/身子不想动)


slumberous: may replace any of the other terms; distinctively it may connote quiescence or the repose of latent powers: felt the sea's ~ power.  （quiescent暂时停止静止沉寂suggests a usually temporary cessation of activity, 如political tensions were quiescent at the moment政治紧张氛围暂时停止了）


sleepy瞌睡: 泛指想要睡觉的或使人想要睡觉的，drowsy昏沉: 强调瞌睡带来的昏沉慵懒，而非真的需要睡觉，somnolent困倦: 强调瞌睡带来的迟缓懒惰， 而非真的想要睡觉，slumberous: 特指潜在力量的暂时沉寂休息


记忆方法: 1）首字母SDSS想成死死地睡<==瞌睡

         2）瞌睡的意思是想睡觉或使人想睡觉mean affected by or inducing a desire to sleep.  （induce表示影响或引发to influence someone to do something or to cause something，如induced them to vote for her proposal力促他们投票支持她的建议，如doctors said surgery could induce a heart attack医生们说手术有可能引起心脏病发作)