1、作动词，意为“回答，答复”。

He didn't reply. Instead, he turned on his heel and left the room. 

他没有回答，反而转身离开了房间。

2、作名词，意为“（口头或书面）回答，答复；回应，作出反应”。

They received a negative reply. 

他们得到一个否定的答复。

3、in reply   作为答复，回答

He said in reply that the question was unfair. 

他回答说这个问题不公平。

4、reply for sb.   代表某人作答

There are too many people, therefore I will reply for you. 

这里有太多人了，所以我会替你回答。