Cách dùng dấu phẩy (Commas)

Commas with Numbers (Số)

Use commas to separate off the thousands and millions in compound numbers.

Example: 3,460,759


Don’t use commas in decimals.

Example: $3.49


Use a comma before the year if the date is given as follows: month, day, year.

Example: April 16, 2003


Don’t use a comma if only two elements of the date are given (e.g. month and year).

Example: I was born in May 1972.


Commas with Salutations (Chào hỏi)

Use a comma if the sentence starts with an address to someone.

Example: Greg, can I talk to you for a second?


Use a comma with salutations in private letters.

Example: Dear Francis,


Don’t use a comma with salutations in business letters.
Use a colon ( : ) in American English and
no punctuation mark in British English.

Example:
BE – Dear Mr Jefferson
AE – Dear Mr. Jefferson:


After the greeting, the comma is optional.

Example:
Sincerely,
Sincerely


Commas with Geographic Places (Tên địa danh)

Use a comma to separate parts of geographic places. The final comma is optional.

Example: Hollywood, Ireland(,) is not as famous as Hollywood, California.


Use a comma to separate parts of an address in a sentence.

Example: His address is 46 Baker Street, London, NW2 2LK, Great Britain.


Commas with “please” (Cách dùng với "please")

Use a comma if “please” is at the end of a request.

Example: Send me a mail, please.


Don’t use a comma if “please” is at the beginning of a request.

Example: Please send me a mail.


Commas with Affirmatives, Negatives and Question Tags (Câu khẳng đinh, câu phủ định và câu hỏi đuôi)

Use a comma after “yes” and “no”.

Example: Yes, I can help you.


Use a comma before question tags.

Example: You are Scottish, aren’t you?


Commas with Adjectives (Tính từ)

Use a comma if the adjectives are equally important and give similar kinds of information.

Example: It was a cold, windy morning.


Don’t use a comma if the adjectives are not equally important or give different kinds of information.

Example: He was a clever young man.

Note:

To check if adjectives give similar kinds of information or not, put and between the adjectives. (It was a cold and windy morning.)

If adjectives give different kinds of information, the and between the adjectives doesn't sound right. (He was a clever and young man.)



Commas with Adverbs (Trạng từ)

Use a comma after certain adverbs: however, in fact, therefore, nevertheless, moreover, furthermore, still, instead, too (meaning 'also').

Example: Therefore, he didn't say a word.


If these adverbs appear in the middle of a sentence, they are enclosed in commas.

Example: The thief, however, was very clever.


The comma is optional for the following adverbs: then, so, yet.

Example:
So, she entered the house.
So she entered the house.


Commas with Enumerations (Liệt kê)

Use a comma to separate items in an enumeration.

Example: Old McDonald had a pig, a dog, a cow, a horse.


The comma before “and” is optional. (Choose the option you like best and stick to it.)

Example:
Old McDonald had a pig, a dog, a cow and a horse.
Old McDonald had a pig, a dog, a cow, and a horse.


Don’t use a comma before “and” if two items are a unit (“Ham and eggs” as a dish is a unit and should therefore not be separated by a comma.)

Example:
Old McDonald had soup, ham and eggs and apple pie for dinner.
Old McDonald had soup, ham and eggs, and apple pie for dinner.


Don’t use a comma if all items in an enumeration are separated by “and”, “or”, “nor” etc.

Example:
Old McDonald had a pig and a dog and a cow and a horse.
Old McDonald had a pig or a dog or a cow or a horse.
Old McDonald neither had a pig nor a dog nor a cow nor a horse.


Commas between Main Clauses (Mệnh đề)

Use a comma between two main clauses which are separated by and or but.

Example: We ran out of fuel, and the nearest petrol station was 5 miles away.


Use a comma to separate parts of a sentences in a sequence.

Example: She ran down the stairs, opened the door, saw her boyfriend(,) and gave him a kiss.


Don’t use a comma if these parts of the sentence are separated by and or but.

Example: She ran down the stairs and opened the door and saw her boyfriend and gave him a kiss.

Note: Don’t use a comma, but a semi colon (; ), if two main clauses are not separated by and or but.


Commas with Conditional Sentences (Câu điều kiện)

Use a comma if the if clause is at the beginning of the sentence.

Example: If I go to London, I will visit the Tower.


Don’t use a comma if the if clause is at the end of the sentence.

Example: I will visit the Tower if I go to London.



Commas with Direct Speech (Câu trực tiếp)

Use a comma after the introductory clause.

Example: She said, “I was in London last year.”


If the direct speech is at the beginning of the sentence, put the comma before the final quotation mark (" "). (Don’t use a full stop here.)

Example: “I was in London last year,” she said.


Don’t use a comma after direct speech if the direct speech ends with a question mark (?) or exclamation mark (!).

Example:
“Were you in London last year?” he asked. (but: He asked, “Were you in London last year?”)
“Great!” she replied. (but: She replied, “Great!”)


Commas with Introductory Clauses

Use a comma after introductory infintive clauses.

Example: To improve her English, she practised on ego4u every day.


Use a comma after introductory prepositional clauses.

Example: Before he went to New York, he had spent a year in Australia.


Use a comma after introductory participle clauses.

Example: Having said this, he left the room.

Note: In short introductory sentences, the comma is optional and can be dropped.


Commas with Additional Information (Thêm thông tin)

Use a comma if the additional information is not part of the main statement.

Example: Thank you, ladies and gentlemen, for giving me the opportunity to speak to you today.

Note:
Depending on the importance attached to it, additional information can be enclosed in brackets, commas or dashes.

Brackets – not important
Connor (Amy's boyfriend) bought the tickets.

Commas – neutral
Connor, Amy's boyfriend, bought the tickets.

Dashes – emphasised
Connor–Amy's boyfriend–bought the tickets.

Relative clauses - Mệnh đề quan hệ

Use a comma in relative clauses before who and which if the information is not essential for the understanding of the sentence.

Example: Her brother, who lives in Chicago, came to see her.She has only one brother. He lives in Chicago and came to see her.


Don’t use a comma in relative clauses if the information is essential for the understanding of the sentence.

Example: Her brother who lives in Chicago came to see her. She has more than one brother. But she was visited by only one of them–the brother who lives in Chicago.


Don’t use a comma if the relative clause starts with that.

Example: The book that I’m reading now is interesting.


Commas with Opposites

Use a comma with opposites, even if they are separated by and or but.

Example: It was the father, and not the son, who went to the disco every Friday.


Commas as Means of Readability

Commas help to keep the structure of the sentence clear so that the text is easy to read and understand. A text is well structured if the reader knows where to pause.

Beispiel: Above, the eagle flew gracefully through the air.

Note: Without the comma, the sentence might be confusing for the reader as the first three words can be seen as a unit (“Above the eagle …”). Of course, the sentence does not work this way, but the reader might have to read the sentence again to get the message. Using a comma after “above”, the author makes the sentence easier to read and understand.
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