单词都是有一个出现的频率的，有些单词的意思常见，但是不常考，有些是常考，但是不常见。atmosphere就属于那种常见词义不考的。我们中国的单词书里面总喜欢把“大气”的词义放在前面，但是生活之中常见的词义是“气氛”。不过在托福考试iBT之中“气氛”“大气”这两个词义出现的频率该都在50%。
/ ˈætməsfɪə(r); ˋætməsˏfɪr/ n
(a) the atmosphere [sing] the mixture of gases that surrounds the earth 大气, 大气层（包围地球的气体）. (b) [C] mixture of gases that surrounds any planet or star 包围任何星球的气体: the moon's atmosphere 月球周围的气体 * an atmosphere that supports life 可以维持生命的气体.
[sing] air in or around a place 某一地方的空气: The atmosphere is very stuffy in here can we open a window? 这里的空气很闷--咱们能把窗户打开吗?
[sing] feeling in the mind that is created by a group of people or a place; mood 气氛; 情绪: An atmosphere of tension filled the room. 屋子里笼罩着紧张的气氛. * The atmosphere changed as soon as she walked in. 她一进来气氛就变了. * The atmosphere over dinner was warm and friendly. 用餐时洋溢着热情友好的气氛.