全文颜色说明

red代表与小标题相关的关键信息。
blue代表与小标题无关的重要信息。
green代表自己归纳出的对自己很关键的信息。

1. 逗号

A. 一个句子由2个分句组成，如果第二个分句由连词(and, but等)，as, for, nor, while引导，连词前面需要用逗号分开。

The early records of the city have disappeared, and the story of its first years can no longer be reconstructed.

B. 如果一个插入语（一个从句或者一个需要逗号分开的引导性短语）位于第二个独立分句之前，则连词后不需要逗号。

The situation is perilous, but if we are prepared to act promptly, there is still one chance of escape.

if we are prepared to act promptly这个从句位于第二个独立分句there is still one chance of escape之前，根据插入语的特点，此时从句前后均需要逗号，但此时前面的逗号省略。

C. 当2个分句的主语相同并且只出现一次时候，连词but前逗号不可以省略；但连词and连接的前后两部分关系紧密时，可以省去逗号。

I have heard his arguments, but am still unconvinced.
He has had several years’ experience and is thoroughly competent.

注：连词连接的2个分句，即使主语和谓语相同，但仅可以删去第二个分句的主语，其谓语必须保留

D. 不要把句子拆成2半, 应该用逗号时不要用句号。

I met them on a liner many years ago. Coming home from Liverpool to New York.
I met them on a liner many years ago, coming home from Liverpool to New York.

E. 允许把一个强调的词或者词组用作句子，并相应的用句号结尾。

Again and again he called out. No reply.

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F. 由一个连词连接的三个或者三个以上的一组词语中，除最后一个外，其余的每个词语后面都需要用逗号分开。

red, white, and blue
He opened the letter, read it, and made a note of its contents.

2. 分号

A. 不要用逗号连接独立分句，建议用分号。两个或者两个以上，语法上面完整且不用连词连接的分句构成一个并列的复合句时，用分号连接比较恰当。

It is nearly half past five; we cannot reach town before dark.

其实这个句子也可以用连词连接，但这用分号连接更加简洁，有力。

It is nearly half past five, and we cannot reach town before dark.

B. 如果第二个分句之前不是连接词，而是副词，如：accordingly(相应的，从而)、besides(而且，此外)、then(然而)、thereforce(因此)和thus(因而)，用分号连接比较恰当。

I had never been in the space before; it was dark as a tomb.

特例：
C. 如果各个分句都很短且形式相似，或者整个句子的语气比较随便，则可以用逗号。

Man proposes, God disposes.(谋事在人，成事在天)
Here today, gone tomorow.(来也匆匆，去也匆匆)
I hardly knew him, he was so changed.(很口语化)

3. 冒号

A. 冒号的作用—在一个独立分句之后引导一系列的事物
在独立分句之后用冒号来引导一系列具体的事物，一个同位语，一个进一步阐述的词语或者一条说明性的引语。其后面部分和前面的分句是密切相关的，冒号的作用比逗号强，比破折号正式，但其分割作用不如分号。冒号通常位于独立分句之后，但不应置于动词和其宾语或介词和其宾语之间。

Your dedicated whittler requires: a knife, apiece of wood, and a back porch. (错误表达)
Your dedicated whittler requires three props: a knife, apiece of wood, and a back porch.(动词和其宾语不能分开)

B. 冒号的作用—在一个独立分句之后对其进行解释的同位语或者分句
有2个独立分句，如果第二个分句是对第一个分句进行解释或者进一步阐述，则用冒号连接。

But even so, there was a directness and dispatch about animal burial: there was no stopover in the undertaker’s foul parlor, no wreath or spray.

C. 冒号的作用—在一个独立分句之后对其说明性的引语
冒号还可以用来引导依据佐证或说明前面一个分句的引语。

The squalor of the streets reminded him of a line from Qscar Wilde: “We are all in gutter, but some of us are looking at the stars.”

D. 冒号的作用—表达某些特定的形式
超级正式函件称呼之后的冒号，表明时间的小时和分钟之间的冒号。书名和副标题之间的冒号，以及《圣经》各章节之间的冒号，在形式上都有分隔作用。

Dear Mr. Montague:
departs at 10:48 P.M. （开车）
Pratical Calligraphy: An Introduction to Italic Script
Nehemiah 11:7 (圣经第十一章第七节)

4. 破折号

A. 破折号表示突然停顿或者中断，引导一个较长的同位语或简短的总结。破折号的分隔作用比逗号强，但不如分号正式，又不如圆括号严谨。只有当普通的标点符号似乎都不适用的时候，才使用破折号。

His first thought on getting out of bed — if he had any thought al all —- was to get back in again.
Violence, the kind you see on the television, is not honestly violent. there lies it harm.
Violence—-the kind you see on the television—-is not honestly violent—-there lies it harm.