逗号(comma)是英语书写中的非常重要的标点符号，它的用法和中文中的逗号差不多，但有所不同，下面进行了一些用法的整理：
1.用于分隔并列成分(In lists)
To avoid confusion, use commas to separate words and word groups with a series of three or more.
为了避免混乱，用逗号分隔三个或三个以上并例的单词或词组。
Example:
My $10 million estate is to be split among my husband, daughter, son, and nephew.
我的1000万美元财产将分给我的丈夫、女儿、儿子和侄子。
2.用于并例的两个形容词之间
Use a comma to separate two adjectives when the word and can be inserted between them.
当两个形容词修饰一个名词时，中间用逗号分隔。
Examples:
He is a strong, healthy man.
他是一个健康强壮的男人。
We stayed at an expensive summer resort.
我们住在一个昂贵的避暑胜地。
You would not say expensive and summer resort, so no comma.
你不能说昂贵避暑的圣地，所以不用逗号。这里昂贵是修饰避暑圣地。
3.用于分隔-ly形容词和其它形容词
Use a comma when an -ly adjective is used with other adjectives.
当一个-ly形容词与其它形容词一起用时用逗号分开。
NOTE:
To test whether an -ly word is an adjective, see if it can be used alone with the noun. If it can, use the comma.
测试其中的一个-ly单词是否是形容词，看他是否可以单独用于一个名词，如果可以，用逗号。
Examples:
Felix was a lonely, young boy.
菲利克斯是个孤独的小男孩。
I get headaches in brightly lit rooms.
在灯火通明的房间我头痛
Brightly is not an adjective because it cannot be used alone with rooms; therefore, no comma is used between brightly and lit.
Brightly不是一个形容词，因为他不能单独用于修饰房间；因些，在brightly和lit.之间没有逗号。
4.用于直呼人名或头衔之前或前后。
Use commas before or surrounding the name or title of a person directly addressed.
在直接称呼的人的姓名或头衔之前或周围使用逗号。
Examples:
Will you, Aisha, do that assignment for me? 你，艾莎，做我给你的事吗？
Yes, Doctor, I will. 是的，医生，我会的。
NOTE:
Capitalize a title when directly addressing someone.
直接称呼某人时大写。
5.用于分隔“月日年”格式表达日期
Use a comma to separate the day of the month from the year and after the year.
在“月日，年”格式表示日期时，用逗号分隔日和年。
Example:
Kathleen met her husband on December 5, 2003, in Mill Valley, California.
2003年12月5日，凯思琳在加利福尼亚米尔山谷遇到了她的丈夫。
If any part of the date is omitted, leave out the comma.
如果省略了日期的任何部分，请省略逗号。
Example:
They met in December 2003 in Mill Valley.
他们2003年12月在米尔山谷相遇。
6.用于地址分隔城市和省（州）
Use a comma to separate the city from the state and after the state in a document. If you use the two-letter capitalized form of a state in a document, you do not need a comma after the state.
NOTE: With addresses on envelopes mailed via the post office, do not use any punctuation.
Example:
I lived in San Francisco, California, for 20 years.
I lived in San Francisco, CA for 20 years.
7.名字或标题周围逗号使用
Use commas to surround degrees or titles used with names. Commas are no longer required around Jr. and Sr. Commas never set off II, III, and so forth.
Example:
Al Mooney, M.D., knew Sam Sunny Jr. and Charles Starr III.
8.用于分隔句子流。
Use commas to set off expressions that interrupt sentence flow.
用逗号隔开中断句子流的表达式。
Example:
I am, as you have probably noticed, very nervous about this. 正如你可能注意到的那样，我很紧张。
9.强调句放在后面，前句用逗号分开。
When starting a sentence with a weak clause, use a comma after it. Conversely, do not use a comma when the sentence starts with a strong clause followed by a weak clause.
当以一个弱句开始一个句子，在弱句后面用逗号，相反地，当以强调句开始句子则不用逗号。
Examples:
If you are not sure about this, let me know now. 如果你对此不太肯定，现在就告诉我。
Let me know now if you are not sure about this. （注意这两句话的区别，后句强调告诉我！）
10.用于短语之后
Use a comma after phrases of more than three words that begin a sentence. If the phrase has fewer than three words, the comma is optional.
以超过三个单词的短语开始句子，短语之后要用逗号，如果短语少于三个单词，逗号是可选的。
Examples:
To apply for this job, you must have previous experience. 要申请这份工作，你必须要有经验。
On February 14 many couples give each other candy or flowers. 2月14日，许多夫妇互相送糖果或鲜花。
OR
On February 14, many couples give each other candy or flowers.
11.用在充分了解的人或事之后
If something or someone is sufficiently identified, the description following it is considered nonessential and should be surrounded by commas.
如果某事或某人已被充分了解，后面紧跟的被认为是不必须的描述应该被逗号包围。
Examples:
Freddy, who has a limp, was in an auto accident.
弗莱迪在一次车祸中瘸了。
Freddy is named, so the description is not essential.
弗莱迪被命名，所以描述不是必需的
The boy who has a limp was in an auto accident.
那个男孩 在一次车祸中瘸了。
We do not know which boy is being referred to without further description; therefore, no commas are used.
我们不知道哪个男孩未经进一步说明就被提及，因此，没有使用逗号。
12.用逗号分隔两个长的分句
Use a comma to separate two strong clauses joined by a coordinating conjunction--and, or, but, for, nor. You can omit the comma if the clauses are both short.
用逗号分隔两个由连词连接的比较长的分句，如果两个分句都比较短可以省略逗号。
Examples:
I have painted the entire house, but he is still working on sanding the doors. 我已粉刷了整个房子，但他仍在打磨门窗。
I paint and he writes. 我画画，他写字。
13.用逗号分隔两个句子。
Use the comma to separate two sentences if it will help avoid confusion.
如果两个句子连在一起可能引起混乱，用逗号分隔两个句子。
Example:
I chose the colors red and green, and blue was his first choice. 我选择了红色和绿色，蓝色是他的首选。
14.
A comma splice is an error caused by joining two strong clauses with only a comma instead of separating the clauses with a conjunction, a semicolon, or a period. A run-on sentence, which is incorrect, is created by joining two strong clauses without any punctuation.
Incorrect:
Time flies when we are having fun, we are always having fun. (Comma splice)
Time flies when we are having fun we are always having fun.(Run-on sentence)
Correct:
Time flies when we are having fun; we are always having fun.
OR
Time flies when we are having fun, and we are always having fun. (Comma is optional because both strong clauses are short.)
OR
Time flies when we are having fun. We are always having fun.
15.用于引语之后
Use commas to introduce or interrupt direct quotations shorter than three lines.
少于三行的介绍或打断直接引语用逗号分隔。
Examples:
He actually said, "I do not care." 他居然说：“我不关心”。
"Why," I asked, "do you always forget to do it?" “为什么，” 我问？“你总是忘记做这件事吗？”
16.用于分隔问题的陈述部分
Use a comma to separate a statement from a question.
用一个逗号分隔一个问题的陈述部分。
Example:
I can go, can't I? 我可以去，不是吗？
17.用于分隔句子的对比部分
Use a comma to separate contrasting parts of a sentence.
用逗号分隔句子的对比部分。
Example:
That is my money, not yours. 那是我的钱，不是你的。
18.用于介词开始句子的介词后
Use a comma when beginning sentences with introductory words such aswell, now, or yes.
当用如aswell,now或yes之类的介词开始句子时，介词之后要用逗号。
Examples:
Yes, I do need that report. 是的，我确实需要那份报告。
Well, I never thought I'd live to see the day . 恩，我从没想过我会活到今天。
19.用于阻碍句子的单词两边
Use commas surrounding words such as therefore and however when they are used as interrupters.
阻碍句子的单词如therefore、however两边用逗号分隔。
Examples:
I would, therefore, like a response. 因此，我想得要一个回应。
I would be happy, however, to volunteer for the Red Cross. 然而，我愿意为红十字会志愿工作。