非谓语动词有三种形式：
动词不定式 to do sth ,表示将来
现在分词 doing sth,表示主动和现在,
过去分词 done sth,表示被动和完成.
一般非谓语动词可以充当定语,状语等成分.看句子的具体需要.
例如 The boy standing beside me is my brother,这里是现在分词做定语.
The school to be built lies in Guangzhou,不定式做后置定语.
Tied with his hands,the thief was caught by him.过去分词做状语.