表示转折关系的并列连词。

主要有 but(但是), yet(可是), while(而，却)等。如：

I would have written before but I have been ill. 我本该早写信的，但我生病了。

I have failed, yet I shall try again. 我失败了，但我还要尝试。

You like tennis, while I’d rather read. 你爱打网球，但我爱看书

Someone borrowed my pen, but I don’t remember who. 有人借了我的钢笔，但我不记得是谁了。

He said he was our friend, yet he wouldn’t help us. 他说他是我们的朋友，但却不肯帮助我们。