It was raining so hard that they could not work in the fields.

    They could not work in the fields because it was raining hard.

    It was raining hard, so they could not work in the fields.

    As it was raining hard, they could not work in the fields.

    误：The essay is poorly organized, there is no central idea.

    正：The essay is poorly organized; there is no central idea.

    The essay is poorly organized: there is no central idea.

五、：冒号

    1.冒号用于对后面内容的介绍或解释，如 This is her plan: go shopping.

    2.冒号用于名单之前，特别是一个竖排的名单。

    We transferred three employees to new branches:

    • Tony Wang to New York City

    • Mike Jackson to Tokyo

    • Mark Foster to Paris

    当名单横排的时候，冒号要用在一个完整的句子之后，如 We need seven people: three students, three engineers, and a professor.

    3.冒号用于一个正式的引用之前。如 The professor said: “It was horrible.”

    4.冒号也可用于商业或正式信函的称谓后面，如 Dear Mr. Lee:(美国英语中，信件或演说词的称呼语之后用冒号，而在英国英语中多用逗号。)

    5.冒号用于数字时间的表示，如16:45 或 4:45 p.m.

    6.冒号用于主标题和副标题之间，如 Web Directory: World and Non-U.S. Economic Data

    六、，逗点

    1.逗点用于分隔一系列的简单内容，如 I will go to Shanghai, Beijing, and Shenzhen.

    2.逗点用于修饰名词的多个形容词之间，如 a small, fancy bike

    3.逗点用于连接两个较长的独立子句，而且每个句子的主语不同，如 The Grizzlies were out of timeouts, and Miller missed a desperation 3-pointer as time expired.

    4.逗点用于关联的子句之间，如 Since he’s your younger brother, please take care of him.

    5.逗点用于一个较长的修饰短语之后，如 In the middle of the coldest winter on record, the pipes froze.

    6.逗点用于直接引用的句子之前，如 Mary said, “Let’s go fishing.”（注意：这里说的和上面提及的冒号在直接引语中的使用不一样。如果是引用比较正式的发言讲话就要用冒号，一般情况下就用逗点。）

    如果句中含有间接引用就不需要逗点，如 Mary said we should go fishing.

    在反问句之前要使用逗点，如 :

    He worked very hard, didn’t he？

    以上是比较常用的标点,下面列出一些次常用的标点:

    七、连字号Hyphen( -)

    1.连字号主要用于某些前缀(如: self-,ex-和all-) 后和构成复合词。如: liuxuepaper.com