举例说明吧...yet:还...Ihaven'treadityet;

　　while:1,当...时,2.表示对比的...heisplaying,whileIamreading.

　　however和but的区别：But在文法上是一个连接词,即用来连接两句完整句子的字；但however只是个adverb,不能用来连接句子.而用however时要用comma把它从句子其他部份分开.简单例子：

　　Iloveher,butshedoesn'tloveme.

　　如果换上however就错了文法.要开新句才可用however：

　　Iloveher.However,shedoesn'tloveme.

　　However可用於句子中间,用作加强语气的interruption.其实这才是however最好用的地方.英文写作专家WilliamStrunk在其巨著"TheElementsofStyles"写道：永远不要把however放在句子开头(however另外一个用法除外).