逗号（Comma）

在复合句中，逗号用于在连词前（如：and, but ,or, for, so,nor,or yet）进行分隔，例如：

We are tired, and we decided to have a rest.

并列的句子为独立的短句、简单句，在意义上具有联系时，也可以不用连词，直接用逗号连接，例如：

A memoir is history, it is based on evidence.

状语从句（包括介词短语、分词短语等）时，逗号通常位于从句之后，主语之前或置于句子中间，例如：

When the bell rang, the teacher dismissed the class.

To see the importance of this railway, one has to look at a map.

状语从句较短或者不使用逗号不会引起歧义的情况下可以不使用逗号，例如：

In one corner of the room they found the injured cat.

状语从句跟在主句之后也可以不使用逗号，例如：

He found the document in one of the drawer of his desk.

逗号用于分隔一系列具有相同功能的单词或短语，例如：

The little girl likes to sing, to dance, and to act.

非限制性从句和短语用逗号隔开，例如：

Wang Li, who is the best singer of the class, will teach us to sing the song.

逗号用于标示括号内的元素，例如：

The director, in fact, has done very little work..

句号（Period）

句号用于结尾的陈述句、较弱的命令句和间接疑问句，例如：

The period marks the end of a sentence..The next word, if you go on writing, has to be capitalized because it begins a new sentence.

句号常用在缩写中，例如：

Mr. Mrs. Dr. U.S.A. a.m. p.m. U.K. B.A.

但现在在使用缩写时通常把句号省略，尤其是用于组织机构的名称等时，例如：

NBA UNESCO NATO BBC NBC YMCA

三个空格的句号（即省略号）用来表示省略或表示说话间的停顿等，例如：

“What do you mean?”

“I meann…well, I mean you needn’t be involves in it.”

如果省略号位于句子结尾，后面应使用句号，因此四个句号一起使用。

分号（Semicolon）

分号用于在两个独立的主从句之间进行分割，不通过连词连接（如：and, but, or, nor, for, so, yet），例如：

No one is born with knowledge; knowledge must be taught and learned.

分号用于连接带内部分隔符的从句，例如：

Unfortunately, Wang couldn’t come; and his absence made things difficult for us.

分号用于分隔包含内部逗号的一系列项目，例如：

On the committee are quite a few well-known people; for example, Professor Zhao, Dean of the Normal College; Mr.Han, editor-in-chief of the local evening paper; and Mr.Hu, Director of the Bureau of Culture.

分号可能连接一个从句与省略的词语；有时通过逗号表示省略的部分，例如：

Five students from Class 1 won prizes in the competition; two from Class 2; none from Class3.

There are four Nobel Prize winners in their university; in our university, none.