在英语中，我们常用so替代上文中提到的某些成分来避免重复。
　　1. 替代形容词
　　①They are very busy now and will remain so for some time. （so替代very busy）
　　②John wears his hair very long and likes keeping it so. (so替代very long)
　　2．替代名词
　　①Mr. Smith is a doctor. He became so after he graduated from college. (so替代a doctor)
　　②——He is an honest man.
　　——Yes, so he is. （so替代an honest man）
　　3．替代介词短语
　　①——He entered our room without knocking at the door.
　　——He often comes in so.
　　(so替代 without knocking at the door)
　　②All the children are in a good state of nutrition, and we must keep them so.
　　（so替代in a good state of nutrition）
　　4．替代副词
　　①——We are walking a little slowly, I am afraid.
　　——Don’t worry.They are walking so.
　　(so替代 a little slowly)
　　②He can speak English well while I can write it so. （so替代well）
　　5．替代动词
　　①If she asks me to attend her birthday party, I will do so.
　　(do so替代attend her birthday party)
　　②They decided to go to Tibet, and they did so.
　　（did so替代went to Tibet）
　　6．替代句子
　　在believe, think, guess, hope, imagine, suppose, expect, fear, it seems, it appears, be afraid, if, why
　　等后接so（表示肯定）或not（表示否定）替代某些句子。
　　①——Is she a nurse?
　　——I think so. (so替代She is a nurse.)
　　②Will that be enough? If so, do not ask more.
　　（so替代That will be enough.）
　　③——I don't like her.
　　——Why not? (not替代You don't like her.)
　　④——The students are reading books in the reading-room, are they?
　　——I guess not.
　　(not替代The students are not reading books in the reading-room.)
　　另外，believe, think, suppose, imagine, expect, say等可构成not…so句型。
　　①——Do you think it's going to rain over the weekend?
　　——I don't believe so.
　　（so替代it's going to rain over the weekend）
　　②——Will mankind land on Mars in ten years?
　　——I don't imagine so.
　　(so替代Mankind will land on Mars in ten years.)