dark: the general term, implies utter or virtual lack of illumination: a ~ cave. (illumination照明启迪彩图，词根LUM表示light光，如lumen流明是物理中光的单位，luminary名人，luminous发光的光彩的，bioluminescent生物发光的如firefly萤火虫和most deep-sea animals大多数深海动物)      （virtual.实际上的实质上implies a merely apparent difference between outward seeming and inner reality只是看起来有些不同，如the prime minister is the virtual ruler of his country首相是实际上的统治者，如本例virtual lack of…实际上缺乏光线，可能有少量光线，但无实质差别， 在计算机方面virtual意思完全不同，表示虚拟的，指通过软件模拟的，你以为看到某物实际上没有，如virtual reality虚拟现实,virtual library虚拟图书馆, virtual shop虚拟商店）


dim: suggests too weak a light for things to be clearly visible: a clandestine meeting in a ~ bar.  


dusky: suggests deep twilight and a close approach to darkness: trudging through ~ woods at day's end.  dusk黄昏 （twilight黄昏或暮光，即日落后剩余的微弱光线small amount of light after the sun has gone down，如the deepening autumn twilight渐浓的秋日暮色）  （trudge徒步跋涉。步履沉重to walk slowly and with heavy steps，如it was a hard trudge up the hill这趟上山是艰难的跋涉）


murky: implies a heavy obscuring darkness such as that caused by smoke, fog, or dust in air or mud in water: fish cannot live in the river's ~ waters.


gloomy: implies serious interference with the normal radiation of light and connotes cheerlessness and pessimism: a ~ room in the basement of the house.


dark黑暗: 通用，表示完全或实际上缺乏光线，dim暗的: 表示光线弱无法看清东西，dusky昏暗: 表示日落已深接近全黑(dusk黄昏)，murky混浊: 表示混浊不清，如空气中的烟雾尘水中的泥，gloomy阴暗: 指严重阻挡光线，隐含阴郁悲观


记忆方法：1）首字母DDDMG大大大没光<==黑暗

         2）黑暗的意思是缺乏光线mean more or less deficient in light.