The comma is the most frequently used (and abused) aid to reading. Most poor users of the comma annoy their audience by inserting illogical commas or too many commas, leaving the reader to ponder the author's meaning. Follow a few basic principles, and the use of the comma becomes clear.
To Separate Parts of a Series
Use the comma to separate words, phrases, or clauses in a series. It is a substitute for words such as and, but, and or.
Red, White, Blue, Green
Usually written as:
Red, White, Blue, and Green
It is also used to prevent confusion before the terminating conjunction (in English that means before the last and or or in a long list.
John ate salad, steak and potatoes, and green beans.
He ran across the street, down the sidewalk, and slipped into the bar and grill.
Some nouns, such as tree, glass, and dress are often accompanied by adjectives (descriptive words) that give definite identification:oak tree, wine glass, blue dress.
These phrases are often accompanied by another descriptive word:
tall oak tree, sparkling wine glass, beautiful blue dress.
To call attention to each adjective so that it describes the noun, use a comma to separate them:
a shiny, sleek, red car
To Separate the Clauses of a Compound Sentence
The comma is placed immediately before the conjunction (and, but, for, yet,or, not) to indicate that the conjunction introduces a clause:
Jimmy invited all of his friends to his birthday party, and most of them accepted.
If the sentence is very short, the comma can be left out:
The phone rang and she answered it.
To Separate Interjections and Similar Non integrated Sentence Elements
(1) Use the comma to separate interjections:
Oh, I thought so.
Hey, stop that thief!
Hello, my name is Kasperkatz.
If the interjection occurs in the middle of the sentence, it is separated with two commas:
He tried so hard, alas, he failed.
Use commas to set off other words used as interjections (yes and no are common examples):
No, we can't come.
Terms of direct address:
Mary, come here.
You in the white shirt, get in line.
(2) Use the comma to set off words like: however, moreover, furthermore, therefore, nevertheless and phrases like: on the other hand, in addition, to the contrary.
Nevertheless, we shall persist.
On the other hand, cats are independent
(3) To set off absolute phrases that are not connected to the rest of the sentence
The pond being frozen, we went skating.
It seemed sensible, the day being chilly, to take a jacket.
To Set Off a Long Phrase or Clause Preceding (before) the Subject
When I see a red sky at night, I know tomorrow will be a nice day
If the sentence can be taken in at a glance, the comma is not necessary.
In 1759 she died of the plague.
To Indicate Interruptions of Normal Word Order
Commas must be used to set off any words, phrases or clauses which interrupt normal word order.
The tall and stately oak reached for the clouds.
If, for the purpose of emphasis, the words tall and stately follow the noun tree, they are set off by commas:
The oak, tall and stately, reached for the sky.
A single comma should never interrupt the natural flow of a sentence, but intruding elements of any kind should be indicated by placing a comma before and after:
The year of his birth, 1967, was Canada's centennial.
He was a tall, dark, and to put it mildly, portly man.
To Set Off Nonrestrictive Elements
Any word, phrase, or clause that is not essential to the meaning of the sentence is called nonrestrictive. Set off nonrestrictive elements by commas:
Some words, like February, are difficult to spell.
His father, who is an accountant, is going on a vacation
Make sure that you know the difference between restrictive and nonrestrictive clauses. A restrictive clause, word or phrase is necessary for the reader to understand the meaning:
The people who sat in the front row paid more for their seats.
The clause who sat in the front row is restrictive
Margaret Mitchell's novel, Gone With The Wind, is a classic.
Gone With The Wind was Mitchell's only novel, therefore, its name is not essential
The use of commas indicates whether elements are restrictive or not:
My cat Kasper is black. (The lack of commas indicates that I have more than one cat. One of them is named Kasper.)
My cat, Kasper, is black. (I own only one cat. The name is given but is not essential)
To Separate Contrasted Sentence Elements
Use a comma to emphasize the contrast between two parts of a sentence.
She wanted a red dress, not blue jeans.
He longed for peace, but found conflict instead.
To Prevent Misreading
Soon after, the concert ended.
Without the comma, the reader might well read after the concert as a phrase.
Don't annoy the reader by inserting commas where they are not needed. Commas are intended to help the reader, not confuse him.
WRONG The student insisted, that he had turned in the assignment. [The comma after insisted separates the verb (insisted) from its object (assignment).]
WRONG He spoke in a loud, rumbling, deep, voice. [The comma after deep separates the adjective deep from the word it modifies (voice)]
WRONG The fact that she was only sixteen and not old enough to be out after midnight, was sufficient reason to ground her for a month. [The subject is a long clause, but it is entirely clear. Inserting a comma after midnight merely slows the flow of thought.]
Do Not Separate Words or Phrases Joined by And orOr.
WRONG She went to the fridge, and opened the door. [And joins the compound verb went and opened. It does not join two clauses.]
Do Not Place a Comma Between a conjunction and the Word or Words it Introduces
WRONG John had the flu but, he refused to go home.
WRONG The young man continued to hope that, his girlfriend still cared.
