一、 so作代词时，用来表示前面提到的相同的人，物，事情或情况，常构成下列句式。
1、 so+be(助动词或情态动词)+主语，这一结构用来表示前面所说的情况也同样适用于另一个人或物，意为 in the same way。
The boy died and a week later so did his sister.
I am an English teacher.So is my wife .
但若前面所提到的人或物是两个或两个以上的句子，并且其中既又肯定句，又有否定句；既含实意动词，又含系动词；主语既有表示人的，又有表示物的。这时应用“So it is (was) with”的句式。
Tom studies English well ,but he isn't good at maths.So it is with Kate.
Wang lin is a Chinese girl ,and China is her homeland.So it is with me.
2、so + 主语 + 动词，这一 结构用来表示对上文的情况给予进一步的肯定或确认。
—It was cold yesterday.
—So it was.
—The students study hard.
—So they do .
—He went to college last year .
—So I have heard.
3、主语+动词+so，这一结构意为照前面所说的做了某事或认为，希望，恐怕上文所说的事会发 生。
(1) 主语+do (does,did)+so
He said he would tell me the news,but he did not do so .
(2)主语+hope (expect,think ,believe ,suppose ,imagine ,be afraid) + so
—Do you think his will come ? —Yes ,I think so.
—Will it be fine tomorrow?—I hope so.
注：在用这一结构来代替否定概念时 ，既可用so，亦可用not，在动词believe，expect，suppose，imagine，think 等的肯定形式后加not与否定形式后加so，两者在意义上没有区别。但在hope，be afraid 后代替否定概念时只能是not，而不能用so。
—Will he come here ? —No,I suppose not .(No,I don't suppose so.)
—Will you get the first prize? —I'm afraid not.(不说I'm not afraid so.)
4、so也可用在if 后面，用来代替前面的内容，表示省略了一个从句。
Are you free this afternoon ?If so ,please go shopping with me .
You may have some difficulty in operating the machine at first ,if so, call me at once.
二、so用作副词时，表示程度。意为“这么”，“那么”，常构成下列句式结构：
1、so + 形容词（副词）+that ,引导结果状语从句。
The book is so interesting that we all want to read it .
I was so busy that I had no time to write a letter .
运用这一结构时要注意以下三点：
（1）在so…that…引起的结果状语从句中，一般不用情态动词，但可用can/could.
He ran so fast that I couldn't catch up him.
(2) 在so…that …引起的结果状语从句中，that 可以省略。
He did so well he was pleased by the teachers.
(3)在so …that …引起的结果状语从句中，为了强调，可把so +adj (adv)提到句首，并形成部分倒装。
So excited was the boy that he couldn't speak .
2、so +adj +a\an +n. +that ….和 so+many(much ,few ,little)+n. +that .
He is so busy a man that he has no time to play .
He has so many falls that he was black and blue all over .
3、so that …..,用来引导目的状语从句，其从句中的谓语动词常和can ,may ,might ,should等情态动词连用。
They set out early so that they might arrive in time .
Let's take the front seats so that we may see more clearly .
4、so as to 和so as….to
He stood up so as to see better.
Would you be so kind as to help me?
so的用法
“not so+ adj./adv. (+as...)”表示“不(像)…这么…”; “so+ adj./adv. +that...”用于表示结果; “so+ adj. +a/an+ n. (+as sb/sth)”可用于比较。
so用作连词可用于表示结果,作“因此,所以”解; 也可用于表示目的,作“为了,以便”解; 还可用以引出一段话进行评比。
1、so通常置于所修饰的形容词、副词之前。so修饰“a(an)＋形容词＋名词”时，排列顺序为“so＋形容词＋a（an）＋名词”。
2、so＋系动词（助动词或情态动词）＋另一主语。此句型是主谓倒装结构，表示前句所述肯定情况也适用于另一主语。其中so作“也这样。
3、so＋主语＋系动词（助动词或情态动词）此句型的主语与前一句的主语相同，因而主谓不倒装。
4、主语＋表示看法、意见等动词＋so。在此句型中，so只用于避免重复前面所说过的内容，等于代替肯定的名词性从句。
5、主语＋do+so在此句型中，so和动词do连用，可用来替代上文出现过的动宾和动状结构，以避免重复。