by the way, on the way, in the way

　　(1)by the way 常用作状语，意为"顺便问一下","顺便说一下"。

　　By the way, how old are you?

　　顺便问一下，你多大了?

　　(2)on the way "在……的路上"，后接名词时需加介词to,后接副词home、here、there时不加to。

　　He bought a pen on his/ the way to school.

　　他在上学的路上买了一枝钢笔。

　　(3)in the way "挡路、妨碍"。

　　Your car is in the way.你的小汽车挡路了。