1.so可以用作连词，表示“因此，所以”。

例：I heard some noise outside, so I went out of the room to see why.

so that作为连词词组，表示 “以便，为了”。

例：The vase is put high on the table, so that it won’t be broken.

2.so可以用作形容词，表示“是这样的，是真的”。

例：The newspapers claim she killed him in self defence but that just isn’t so.

3.so可以用作副词，表示——

1)“如此，这么”结构为：so+adj./adv

例：She was so tired that she fell asleep very fast.

表示此意思时，还可以用：so+adj.+a/an+n.

例：It is so good a movie that everyone who saw it praises it very much.

2)“如此，如是”，用于表示已经提到的想法，建议或情况等

例：“Will I need my umbrella?”

“I think so.”

3)“也是，也一样”结构为so+助动词/情态动词/be动词+主语

例：Tony takes exercise every day and so does his younger brother.

注意否定句应把so改为neither/nor，结构为neither/nor+助动词/情态动词/be动词+主语

例：Jenny has never been late for class.Neither/Nor her younger brother.

4)“确实是这样”，表示对前面陈述事实的强调，结构为so+主语+助动词/情态动词/be动词

例：Tony works very hard at all the subjects.So he does.

5)“似乎，那么”，表示惊讶、不同意或者嘲讽

例：So you think you've got troubles?

常见结构：and so on/and so forth：等等;so as to(do)：以便;so that+从句：以便

例：We eat different vegetables， such as tomato，potato，celery，and so on.

They got up early so as to catch the first bus.

They got up so early that they could catch the first bus.