so 作为连词：因此、所以
1.（表因果关系）因此，所以：
- I got ill so I went to see a doctor. 我生病了，因此去看了医生。
2.（引出结果）以致于：
- Nothing more was heard from him so that we began to wonder if he was dead. 此后没有再收到他的消息，以致于我们开始怀疑他是不是死了。
3.（表示目的）为了，以便：
- But I gave you a map so you wouldn’t get lost. 但我怕你迷路，给过你一张地图。
4. 引出下文：
- So after shouting and screaming for an hour she walked out in tears. 就这样，又嚷又叫了一个小时候，她流着泪走了出来。
5. 认为某事无关紧要，尤用于反驳他人的指责时：
- You have been smoking again. 近来又抽烟了。
- So? 抽又怎么了？
6. 引出评论或问题：
- So what have you been doing today? 那么你今天都干什么了？
7. 引出结束语：
- So, that is it for today. 好，今天就到这里。
8. 在问句中代指刚谈论的事：
9. 指出两种情况等相类似：
- Just as large companies are having to cut back, so small businesses are being forced to close. 大公司不得不紧缩，小企业则被迫关闭。
so 作为副词
当然，so 除了连词用法，还可以用作副词，有 “这样、那么” 等含义，这里未再累述。
1. “如此，这么”结构为：so + adj./ adv
- 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.
- It is so good a movie that everyone who saw it praises it very much.
注意与 such 的区别，such + a/an + adj. + n.
- I’ve never seen such a beautiful lake. 我从未见过这么美丽的湖
- a/an 置于 such 之后，但 no, any, some, all, many 等则置于 such 之前
- I’ve heard of some such rumors.
2. “如此，如是”，用于表示已经提到的想法，建议或情况等
- “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
- 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
- Jenny has never been late for class. Neither/Nor has 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
- 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
- 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
- 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.
6. 有时可与并列连词 and 连用，构成习语 and so (相当so):
- He told me to do it and so I did it.他叫我那么做，所以我就做了。
- He worked hard and so he succeeded.他勤奋工作，所以他取得了成功。
- There was so much to eat and so few people to eat it.有这么多东西可吃，而吃的人又这么少。
- l forgot to post the letter, and so she never heard about my divorce.我忘了寄那封信了，所以她一直不知道我离婚的事。
so 作为形容词：是这样的，是真的
- The newspapers claim she killed him in self-defense but that just isn’t so.
补充：不要按汉语意思将 “因为...所以.…” 直译为 because...so... :
- × Because he was ill, so he couldn't come.(去掉 because 或 so 中任意一个)