air: refers to the impalpable breathable substance essential to life: the ~ we breathe; or that substance mixed with others: smoggy ~.          如high in the mountains the air is thin高山空气稀薄，如to travel by air飞行旅行


atmosphere: suggests the gaseous layers surrounding the earth or another celestial body: the poisonous ~ of Venus; or the air which fills a particular place or is in a particular state: the room's stagnant ~.     celestial body天体      氛指香气，在气氛、氛围中表示气体


ether: implies a more rarefied or more delicate or subtle medium which was formerly said to fill the upper regions or interstellar space: gods who dwelled in the ~; and is used technically to denote a hypothetical medium in space suitable for the transmission of transverse waves: broadcast into the ~ in hopes someone would hear.      (delicate表示精致微妙纤弱 implies exquisiteness,subtlety or frailty，如the play's delicate charm was lost onscreen剧本的微妙魅力在荧幕上消失了，形容味道气味时表示柔和淡雅pleasant,not intense or strong，如young haricot beans have a tender textureand a delicate, subtle flavour嫩菜豆口感细腻，味道清香淡雅)       subtle微妙implies something difficult to perceive or understand指难以看清理解捉摸的，如Mona Liza's subtle smile微妙的笑容    这里rare, delicate和subtle表示空气稀有淡薄微少          （hypothesis假想假说，如a hypothesis regarding the extinction of dinosaurs恐龙灭绝假说）


ozone: denotes generally air that is notably pure and refreshing: the vivifying ~ of a thunderstorm.        还表示臭氧ozone is a form of oxygen氧气的一种形态


air空气: 指能被呼吸、无法触摸、生命必需的物质或混合物，atmosphere大气层气氛: 指地球周围的大气层，或某地周围的空气，ether以太: 传说中充满太空的稀有淡薄微少的介质，专业上指假想的适合横波传播的介质，ozone新鲜空气臭氧: 指纯净新鲜的空气

记忆方法:  1） 练习一下

           2） 空气的意思是地球周围的不可见的气体混合物mean the invisible mixture of gases which surrounds the earth.