标点符号的运用（Punctuation）
当我们说话时，会提高音亮来加强语气，会停顿来表示语意说毕，而在文字表达上，标点符号便担当着重要的角色，例如：表示句子完结，问句，对话等。有时候，标点符号更可将说话时较难表达的意思提出来，如直接引述别人的语句或文章。如果要读者明白文章内容，便须正确运用标点符号了。
逗号 Comma
逗号是最常用也最常用错的标点符号，其中一个最常见的用法是分开分句（clauses）及短语（phrases）。
（1） 将逗号放于连接词之前a coordinating conjunction（for, and, nor, but, or, yet, so）*，连系两独立子句（independent clauses）。
* 记着：fan boys
例子：
A. The shopkeeper closed his store early, for he wanted to get home.
B.The sky became dark gray, and the air stilled ominously.
C.We cannot expect our laws to be better than we are, nor can we expect our leaders to have higher standards than we have. （原句子：We cannot expect our laws to be better than we are. We cannot expect our laws to be better than we are.）注意：第二子句中要删除 not 及次序倒转。
D.The facts are important, but the truth is essential.
E.High winds will start, or thick snow will begin soon.
F. People on the road tried to reach safety, yet a few unlucky ones were stranded.
G. It was raining heavily, so they gave up dining out.
注意（一）：
如果子句太短及意思相近，可以不用逗号，不过，一般来说，还是使用它较安全。
例子： It is dark and I am alone.
注意（二）：
留意在 compound predicate (double verb) 的句子，不须使用逗号。
例子：
Learning a new language demands time and patience.
The counselors listen to and help many students.
（2） 将逗号放在 an introductory subordinate clause, phrase, or word 之后。
A. Introductory clause:
Though it was hard to believe, the story was true.
B. Introductory phrase:
Eating being enjoyable, we tend to eat more than we need for fuel.
Contrary to popular opinion, this solution is the best.
C. Introductory word:
No, you can't go there.
For example, a car's horn can alert rescuers as far as a mile downwind.
（3） 以逗号分开句子内的 words, phrases, clauses.
例子：
She asked her son to make up and label drawers for each of the following items: toys, stationery, accessories, games, and books.
注意：除特殊情况下，一般来说，在一连串分隔项目中，不要将逗号放在第一项之前或最后一项之后。
错误句子：Many writers, artists, composers, have indulged in daydreaming.
正确句子：Many writers, artists, composers have indulged in daydreaming.
（4） 以逗号来分隔「并列的形容词」 coordinate adjectives（两个或以上形容词用以修饰名词noun 或 noun group）:
例子：
The large, restless crowd waited impatiently for the World Cup to begin.
注意（一）：
不要将逗号最后一个形容词之后，即以上例子中 restless 及 crowd 之间并没有逗号。
注意（二）：
如果两个形容词不是修饰同一名词或不是并列的coordinate，不能在两者之间放逗号。
错误句子：We replaced our old, manual typewriter.
正确句子：We replaced our old manual typewriter.
（5）以逗号来分隔非限制性修饰语nonrestrictive modifiers（或称nonessential element，表示所提供的资料是附加的，虽然资料仍有意义，但在句子中，即使删去此资料，仍没有影响原句子的意思。）
例子：
He dug the potato, which weighed nearly 15 kg, from his garden last year.
注意：不要在限制性修饰语(restrictive modifier） 加上逗号。
错误句子： Stores, which honor credit cards, have noticed an increase in sales.
正确句子： Stores which honor credit cards have noticed an increase in sales.
（句中 which honor credit cards 是不能缺少的部分，如果删去，即指“所有商店都注意到营业额有上升”，而不是原意所指“可以使用信用卡的商店”，所以我们不能用逗号分隔。）
（6）用逗号来分隔同位语 appositives（一个名词或短语解释或补充之前的名词，很多同位语都是非限制性的nonrestrictive，即是说删除同位语也不会影响原句意思。）
错误句子：When I graduate in June, I will begin work at ABC Company a local trading firm.
正确句子：When I graduate in June, I will begin work at ABC Company, a local trading firm.
（7）用逗号来分隔句子中的插入元素 parenthetical elements（插入元素包括字、短语或子句，用以加强或阐明重点，及作出资料补充，由于插入资料干扰了原有句子结构，所以我们会用逗号来分隔开。）
例子：
The family was upset, of course, by little Bowie's eccentric behavior.
American farmers, according to the US government figures, export more wheat than they sell at home.
用逗号来分隔读者或听者的名字 nouns in direct address:
例子：
Jennifer, you have to go to school on time.
用逗号来分隔感叹词 interjections:
例子：
Well, I guess I have no choice in the matter.
用逗号来分隔 tag question:
例子：
He will join us to see the movie, won't he?
（8）用逗号来分隔语次转变 transitional expressions（例如： however, moreover, in fact）
例子：
Therefore, many young people like to watch World Cup with their friends.
（9）用逗号来分隔引述句 quoted words from explanatory words:
例子：
Speaking of ideal love, the poet William Blake wrote, “Love seeking not itself to please.”
“Happy I, that love and am beloved,” said William Shakespeare about reciprocated love.
“I love no love,” proclaimed poet Mary Coleridge, “but thee.”
注意：当引述句结束时用问号或感叹号，要保留原来标点，不须再加上逗号。
引述句： “O, Romeo! Romeo!”
错误写法： “O, Romeo! Romeo,” called Juliet as she stood at her window.
正确写法： “O, Romeo! Romeo!” called Juliet as she stood at her window.
（10）在日期，名称，地址，及数字上使用逗号的要点
I) Dates:
June 1, 2018
Friday, June 1, 2018
注意：如果日期写法是1 June 2018 则不须加逗号。
例子：
Many people wanted to be near a television set on May 31, 2002, to watch the World Cup.
July 4, 1937, was a day he never forgot.
注意：如果日期中只包含月日、年月、或年份季节，则不须加上逗号。
例子：
The major news story during June 2002 was the World Cup; news coverage was especially heavy on June 23.
II) Names and Titles:
Peter Nelson, M.D.
Albert Browns, Jr., took over as chief executive.
III) Places and Addresses:
Toledo, Ohio
141 64th Street, Brooklyn, New York 11212
Working in Orlando, Florida, has many compensations.
IV) Numbers:
246,135,102
$1999 $1,999
1899 miles1,899 miles
1899 hours1,899 hours
1899 potatoes 1,899 potatoes
注意：
年份是不用逗号，如 1997（但会用 25,000 B.C.）
度量上，用逗号来分隔文字，如：five feet, three inches
页数上，则用：page 10, line 5
V) Letter:
Opening of an informal letter:
Dear Mary,
Closing of a letter:
Yours sincerely,
Best regards,
标点符号参考资料：
David & Gerald, Scott, Short English Handbook, Foresman & Co.
Simon & Schuster, Handbook for Writers, Prentice-Hall.
Winkler &McCuen, Writing, Science Research Asso, Inc.
以图片速递方式小结逗号用法
