This page mainly concerns about the uses of different punctuations, especially those easily misused.

1. Definition of the Punctuation:
a mark such as period or comma used in writing to separate sentences and their elements in order to clarify meaning and write in a clear style.


2. Application of Punctuations:
2.1 End punctuation marks- the period, the question mark, and the exclamation point- signal the ends of sentences.
· THE PERIOD is used to end a statement, mild command, or indirect question, and it is also used with abbreviations.
Example
At the end of a statement: I have a computer.
At the end of a mild command: Pass me the book.
At the end of an indirect question: I wonder whether she will come tonight.
With abbreviations: Dr. Mr. Mrs. i.e. e.g.
Note
Use periods with abbreviations that consist of or end in small letters. Otherwise, omit periods from abbreviations. When a sentence ends in an abbreviation with a period, don't add a second periods: My first class is at 8 a.m.
· THE QUESTION MARK is used after a direct question and also is used within parentheses to indicate doubt about the correctness of a number or date.
Example
At the end of a direct question: Where is my ipad?
Within parentheses to indicate doubt: The Greek philosopher Socrates was born in 470 (?) BC and died in 399 BC.
Note
Question marks are never combined with other question marks, exclamation points, periods, or commas:
"Which one is better?," Lisa asks. (Incorrect)
"Which one is better?" Lisa asks. (Correct)
· THE EXCLAMATION POINT is used after an emphatic statement, interjection, or command.
Example
After an emphatic statement: I must finish this assignment today!
After an interjection: Ah! That's it!
After a command: Don't touch anything here!
Note
Exclamation points are never combined with other question marks, exclamation points, periods, or commas:
"I can't stand this anymore!," she roared. (Incorrect)
"I can't stand this anymore!" she roared. (Correct)


2.2 The Comma is used mainly as follows:
· To separate items in a series
Example
The kiosk sells newspapers, magazines, and books.
Note
The final comma in a series is optional, but it is often used.
· To set off introductory material
Example
After the lunch, she continues her work.
Note
If the introductory material is brief, the comma is sometimes omitted.
· On both sides of words that interrupt the flow of thought in a sentence
Example
The hallway, dingy and dark, was illuminated by a bare bulb.
My computer, which my brother got me as a gift, never breaks down.
· Between two complete thoughts connected by and, but, for, or, nor, so, yet
Example
She opened both the window and the door, so the air can circulate in the room.
The purse is the most beautiful one she have ever seen, but it is also the most expensive one.
Note
a. The comma is optional when the complete thoughts are short.
e.g. She feels tired so she stops working.
b. Be careful not to use a comma to separate two verbs that belong to one subject. The comma is used only in sentences made up of two complete thoughts (two subjects and two verbs).
e.g. The doctor stared over his bifocals, and lectured me about smoking. (Incorrect)
The doctor stared over his bifocals and lectured me about smoking. (Correct)
· To set off a direct quotation from the rest of a sentence
Example
"Jim, bring my book to the class today," the note reads.
"I'm sorry," he said, "I just forget to bring the book."
The girl sighed and said," don't forget to bring me the book tomorrow."
Note
Commas and periods at the end of a quotation go inside quotation marks.
· For certain everyday material
a. Persons spoken to: Did you see my ipad, Lisa?
b. Dates: April 13, 2011, is the day I bought my car.
c. Addresses: 1600 Amphitheatre Parkway, Mountain View, CA 94043
Note No comma is used before a zip code.
d. Opening and closings of letters: Dear John, Sincerely yours,
e. Numbers: I want to have a fortune of $500,000 so that I can travel around the world.


2.3 The Semicolon separates equal and balanced sentence elements, usually main clauses, sometimes items in series.
· Between main clauses not joined by and, but, or another coordinating conjunction
Example
The side effects are not minor; some leave the patient quite ill.
Note If you do not link main clauses with a coordinating conjunction and you separate them only with a comma or with no punctuation at all, you will produce a comma splice or a fused sentence.
Exception Writers sometimes use a comma instead of a semicolon between very short and closely parallel main clauses:
The poor live, the rich just exist.
· Between main clauses related by however, for example, and so on.
Example
Blue jeans have become fashionable all over the world; however, the American originators still wear more jeans than anyone else.
Note If you use a comma or no punctuation at all between main clauses connected by a conjunctive adverb or transitional expression, you will produce a comma splice or a fused sentence.
· To separate main clauses if they are complicated or contain commas, even with a coordinating conjunction.
Example
By a conscious effort of the mind, we can stand aloof from actions and their consequences; and all things, good and bad, go by us like a torrent.
--Henry David Thoreau
· To separate items in a series if they are long or contain commas.
Example
The custody case involved Amy Dalton, the child; Ellen and Mark Dalton, the parents; and Ruth and Hal Blum, the grandparents.



2.4 The Apostrophe has two main uses as follows:
  • To show the omission of one or more letters in a contraction
Example
have + not = haven't
I + will = I'll
Note Be aware that many people disapprove of contractions in any kind of formal writing.
  • To show ownership or possession
Example
My sister's book
Jane and Joan's room
Jane's and Joan's toys
Mrs Kims' car
Those boys' bicycles

2.5 Quotation Marks are mainly used in following ways:
  • Use double quotation marks to enclose direct quotations, the exact words of a speaker or writer
Example
"Fortunately," said the girl,"the teacher is busy with other business, so we don't have class this afternoon."
  • Use single quotation marks to enclose a quotation within a quotation
Example
"I went into the room when he cried,'help me.'''
  • Set off quotations of dialog according to standard practice
Example When quoting conversations, begin a new paragraph for each speaker:
"What's your name?"
"Elizabeth."
Note When you quote a single speaker for more than one paragraph, put quotation marks at the beginning of each paragraph but at the end of only the last paragraph, in order to tell readers that the speech is continuing.
e.g. "I want to buy a house......
"I also want to buy a car....
"Actually, I won't buy anything I mentioned above."
  • Put quotation marks around the titles of works that are parts of other works
Example
the essay "On Self-Respect" in the book Slouching Towards Bethlehem
the chapter "Chinese Religion" in the book Paths of Faith
the song "Ziggy Stardust" in the CD Changes
  • Enclose words used in a special sense
Example
It is not easy to find "Mr. Right".
Save your "compassion", I feel comfortable to live my life this way.
  • In the United States, periods and commas go inside quotation marks regardless of logic.
In the United Kingdom, Canada, and islands under the influence of British education, punctuation around quotation marks is more apt to follow logic. In American style, then, you would write: My favorite poem is Robert Frost's "Design." For more information, visit this site:http://grammar.ccc.commnet.edu/grammar/marks/quotation.htm

2.6 Other Punctuation Marks
  • A colon is used at the end of a complete statement to introduce a list, a long quotation, or an explanation. It is also used to separate titles and subtitles and the subdivisions of time.
Example
The library will close on the following dates: April 10, April 11, and April 12.
He supports the girl's opinion in his article:"I agree that we should have more free time for extra-curriculum activities."
I can solve this problem: I know where to buy a new book.
Charles Dicken: An Introduction to His Novels
1:30 AM 12:26 PM
  • A dash signals a pause longer than a comma but not as complete as a period, and it is often used to set off for dramatic effect.
Example
I was so exhausted that I fell asleep within seconds--standing up.
The pardon from Ben finally came--too late.
Note
In your papers, form a dash with two hyphens (--), or use the character called an em dash on your word processor. Do not add extra space around or between the hyphens or around the em dash.
  • Parentheses are used to set off extra or incidental information from the rest of a sentence
  • Brackets are used within quotations to indicate your own comments or changes.
Example
"That Texaco station [just outside Chicago] is one of the busiest in the nation," said a company spokesperson.
  • A hyphen is used to connect two or more words to form a single unit describing a noun.
  • The ellipsis mark is used to indicate omissions from quotations and pauses in speech.

REFERENCE
[1] John Langan, Writing Skills With Readings, 6th Edition, Beijing: Foreign Language and Research Press
[2] H.Ramsey Fowler and Jane E.Aaron, The Little Brown Handbook, 9th Edition, Peking University Press
[3] http://grammar.ccc.commnet.edu/grammar/marks/marks.htm