MPC English & Study Skills Center

Commas

Rule 1

Use commas to separate items in a series or more than two items.  These items may consist of words, phrases, or clauses.  Put a comma before "and."

Words:  I'd like a big bowl of fruit with apples, pears, peaches, and plums.

Phrases:  He liked going to the movies, eating at fancy restaurants, and visiting museums.

Clauses:  She liked him when he was thoughtful, when he was kind, and when he was relaxed.

Hint:  A phrase is a group of words that go together but do not have a subject and verb:  in the morning, running quickly, at noon.

A clause is a group of words with a subject and verb:  John went to the store.

Rule 2

Use commas to separate introductory elements from the rest of the sentence.  These can be words, phrases, subordinate clauses, or transitional phrases.

Words:  Usually, he took a nap after lunch. 
Quickly, he drew his gun and fired.

Phrase:  Coming through the alley, the car swerved to avoid a garbage can.
In the morning, I will go to see the teacher.
After lunch, I went to see the movie.

Clause:  Although he had already eaten dinner, he sat down to have a sandwich.
Because you are my friend, I will help you.

Transitional Expression:  In other words, I'm in love,
On the other hand, meat loaf is fattening.

Note:  The comma is optional after-commonly used introductions of time, such as today, tomorrow, yesterday, now, then, and short prepositional phrases of time, such as on Monday.

Rule 3

Use commas to separate coordinate (or equal) adjectives. To test whether the adjectives are coordinate, reverse the order and put "and" between them.  If they still make sense, they are coordinate.

They were happy, friendly puppies.
Note:  it'scorrect to say "friendly and happy," so these are coordinate adjectives.

They ate at a fancy French restaurant.
Note:  It's not correct to say "French and fancy restaurant," so these are not coordinate and don't need commas.

The following types of adjectives are usually NOT separated by commas:  those that show

Rule 4

Use commas to set off a direct address, that is speaking directly to a person.

Bob, have you seen the report that was on the desk?
I know very well, my friend, that you have done your share.
My child, there is no free lunch.

Rule 5

Use commas to set off an appositive from the rest of the sentence.  When a noun is immediately followed by a groups of words that explains or renames it, the group of words is called an appositive.  An appositive that is set off by commas in not really essential for the meaning of the sentence.

Walt Whitman, a famous American poet, was a very interesting person.

Note:  "A famous American poet" explains who Walt Whitman is, and it is an appositive, but he is already identified by name, so the information is not essential.

Ordinary People, a novel by Judith Guest, is the story about a young boy coming to terms with his brother's death.

Note:   When the appositive consists of only one word, generally a proper noun, that is essential for identification, it is not set off by commas.

My neighbor Natalie is a very dear friend of mine.

My friend Bill is working for the school district.

Rule 6

Use commas to set off parenthetical remarks or interjections:  as a matter of fact, believe me, I as sure, I assure you, in fact, it seems to me, to tell the truth, consequently, hence, first, second, thrid, similarly, oh, wow, well, etc.

He is, I am sure, trying his best.
By the way, you did a very good job.
First, you must do your homework.
Oh, you are so handsome!

Rule 7

Use commas after each part of an address:

He lives at 224 Burnside, San Francisco, California.
I drove to Carmel, California, to see my friends.

Note:  A one-word (or name) address preceded by a preposition (in, on, at, near, from, etc.) is not followed by a comma

He is from New York City on the  East coast.
They went to Fresno for the party.

Rule 8

Use commas after each part of a date.

I arrived on Wednesday, June 16, 1990, in the afternoon.
I was born on December 16, 1944, in Richmond, California.

Note:  a one-word date preceded by a preposition (in, on, at, near, from, etc.) does not need a comma. 

I will go to the prom on Monday after I finish work.

Rule 9

Use commas to achieve clarity, even in places where one might not usually put the, or to emphasis a contrast.

Whatever he did, did not good.
He came to the dance with me, and not with you!

Rule 10

Use commas to set off non-restrictive elements in a sentence.

Restrictive:  necessary for identification (tells which one) and not separated by commas.  One cannot remove a restrictive phrase or clause without losing some of the basic meaning of the sentence.

Never eat apples that are green.  Note:  "that are green" is essential to understanding the meaning.
The woman who is holding a gun is by the door.

Non-restrictive:  gives extra information, but it is not necessary for the basic meaning of the sentence and could be removed.

Steven, although an obnoxious little brat, gets straight A's in school.
Mary Jones, who is wearing a blue dress, is my neighbor.

Note:  "Who is wearing a blue dress" is interesting, but it's not essential to meaning, so it must be set off with commas.

Hint:  That is used only in restrictive clauses and which should be used only in non-restrictive clause (although sometimes people break the rule regarding which).

The dog that bit me has rabies.
My dog, which is very friendly, is not too bright.

Rule 11

Use commas to set off out-of-place adjectives.  Adjectives usually precede the noun in English (the big red balloon), so if the adjectives follow the noun (the balloon, big and red,) they are set off.

The man, tall and mysterious, walked slowly down the street.

Rule 12

Use commas to separate independent clauses joined by coordinating conjunctions:  for, and, nor, but, or, yet, so.

I went to the store, but I forgot to buy milk.
It was very dark last night, and I had to walk home.