1.用于陈述句、（语气温和的）祈使句等

He is a good man.

2.用于某些缩写和小数点后

P.M.（post meridiem）

2.5%

1.分割并列成分

My favorite sports are football, basketball, swimming and golf.

2.分割并列句的分句

He didn't want to go, but he went anyway.

3.分割地点、数字、日期等

Building 911, Sathorn Road, Bangkok, Thailand

1.对后面内容进行延伸解释

There are three countries in North America: Mexico, the USA and Canada.

2.引出或者介绍

There's only one student to pass the test: Jack.

1.分割独立但意思相连的分句

James likes coffee; Mary likes tea.

You did your best; now let's hope you pass the exam.

1.一般疑问句，反义疑问句等

What’s your name?

You’re Chinese, aren’t you?

2.有疑问的陈述句（非正式书写）

He’s your boyfriend?

1.表示感叹、抱怨、惊讶，强调等

She shouted at him,"Go away! I hate you!"

1.用于复合词、复合数字等

ex-boyfriend, up-to-date, thirty-five,

1. 加重说明，突然插入

I'll never forget her name—Celia.

You are the friend—the only friend—who offered to help me.

1.书面或口头直接引语

He said, "I love you."

2.表示强调、突出、反语、标题等等

Have you read "War and Peace"?

1.省略

She’s=she is

2.所有格形式

I’m Lucy’s father.

1.词语或者句子的省略

There are five people in my family. My father is a doctor; my mom is a nurse; my younger sister...

2. 表示停顿、语气拖拉等

He said,"Max, there’s something...I need to tell you. I...love you. "

1.通常表示或者（or)

Dear Sir/Madam (Sir or Madam)

2. 表示“每”

He makes 15 dollars/hour.

1. 附加信息 ( )Parentheses

Tony Blair (the former British prime minister) resigned from office in 2007.

2.添补信息 [ ]Brackets

It is [a] good question.