(1)as 是連詞,意思是"當……的時候,一面……一面",(強調同時,一般連續(xù)時間不長),如:
As we were talking about Titanic, our teacher came in. 正當我們談論"泰坦尼克號"這部電影時,教師進來了。
The students sing as they go along. 學生們邊走邊唱。
(2)When和as一樣都是連詞,注意它們的不同。如when"當……的時候"(一般表示動作緊接著發(fā)生);
"那時"(等立連詞,前有逗號分開)I stayed till sunset, when it began to rain. 我一直呆到太陽下山,那時天開始下雨了。
(3)while是"當……時候;和……同時"(強調同時發(fā)生,一般連續(xù)時間較長)例如:While I was watching TV, he was reading. 當我在看電視的時候,他正在看書。While there is life, there is hope. 有生命就有希望。