1．表转折：
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.
2．表让步：
(1)although：although A, B:尽管有A，B还是出现了（A，B互不影响）若A是正，那B就是负的。
例如：Although the world regards Asia as the focus of an economic and industrial miracle, without adequate supplies of food, Lampe says, chaos could easily result in many countries.
解释：miracle奇迹，表正向,则but后的chaos是一个表负向的词。
(2)while：五个含义：
A．although：虽然，尽管
B．as long as：只要
C．whereas, but：表转折
D．when：当。。。的时候
E．n. 表一段时间
例如：While ducks offer many advantages over hens, they must be given greater quality of food, especially if regular eggs are desired.
解释：原文在本段之前讲鸭子的好，在本段之后讲它的不好。
(3)Albeit：尽管，虽然
例如：Albeit true but not now.