but， however， yet， in fact， on the other hand；

　　A， but B： 否定A而肯定B，则A，B两部分内容是相反的。

　　例如：Computerized data storage and electronic mail were to have heralded the paper less office. But， contrary to expectations， paper consumption throughout the world shows no sign of abating .

　　解释：paper less 表示负向，则but后no sign of abating 表示正向，所以abating是表示负向的词。

　　总结：此种方法有利于在不认识单词的前提下读懂句子意思，很有帮助，但一定要练习，而且要敏感。

　　练习：The marginal costs of generating electricity from nuclear energy may be tiny， but ， as the technology now stands， huge and uncertain costs are involved in building the power stations， dealing with spent fuel， and decommissioning.