谓语动词变为非谓语动词的方法
1、动词后跟-ing，表示主动或者进行（主动居多）。
2、动词后跟-ed，表述被动或者完成（被动居多）。
3、动词前加to，表示目的或者将来（目的居多）。
非谓语动词充当的成分
1、作主语
Example：To finish the work ny yourself is very hard.
< 动词不定式作主语，常用it作形式主语，把真正的主语后置。>
此句变为：
It's very hard to finish the work by yourself.
2、作表语
Her job is to look after the babies.
3、作定语
He enjoys staying with his family.
4、作状语
He worked day and night to get the money.
5、作同位语
His habit,eating snack before sleeping,has not been changed.
