Punctuation Rules

The comma (,)

The comma has several uses in English.

• To separate three or more nouns, verbs, adjectives, etc. that are joined by the following conjunctions: and, or.

Examples: John, Mary, Alice, Bill, and Roger visited the Himalayas last year.

Mary swam ten miles, climbed a mountain, and biked across the Golden Gate Bridge.

Tom plays the flute, the piano, the drums, and the guitar.

Would you like coffee, tea, orange juice, or milk?

However, do not use a comma if there are only two nouns, verbs, adjectives, etc.

Incorrect: Bill Clinton, and Al Gore made an announcement yesterday.

Correct: Bill Clinton and Al Gore made an announcement yesterday.

• To separate two (or three) independent clauses in a compound sentence. (Compound sentences are sentences that have two (or three) independent clauses which are joined by one of the following conjunctions: for, nor, yet, so, and, but, or. The comma always appears just before the conjunction.

Examples: I got a flat tire, so I called a tow truck.

Mary is happy, but Bill is sad, so their son is confused.

• To set off an introductory phrase or transition from the rest of a sentence.

Introductory phrase Example: In 1995, John won six trophies for weightlifting.

Transition Example: Next, he decided to compete in the New York marathon.

If the transition is in the middle of the sentence, it needs a comma on each side:

The traffic, moreover, is terrible.

If the transition appears at the end of the sentence, it needs one comma:

The traffic is terrible, moreover.

• To mark the end of an adverb clause when it begins the sentence.

Example: Because John had the flu, he didn’t go to school.

However, if the independent clause comes first, don’t use a comma.

Example: John didn’t go to school because he had the flu.

• To mark the beginning and end of an appositive if it appears in the middle of a sentence:

Example: Bill Bradley, a former U.S. Senator, used to play basketball.

If the appositive appears at the end of the sentence, it needs only one comma.

Life on earth would not be possible without oxygen, the eighth element on the periodic table.

• To mark the beginning and end of a non-restrictive (non-identifying) adjective clause.

Adjective clauses that appear after people’s names are always non-restrictive.

Example: George W. Bush, who was the governor of Texas, is the President.

The information given is extra, so commas are used to mark it. The sentence will make sense without the clause: George W. Bush is the President

Adjective clauses that appear after something that there is only one of (the sun, the moon, someone’s father or mother) are also non-restrictive.

The moon, which has one-sixth the gravity of the Earth, is usually visible in the sky at night.

However, sometimes we need the information to identify the noun. In that case, do not use commas for the clause.

Example: The man who stole Bob’s luggage had a tattoo of a sailboat on his arm.

Notice that there are no commas setting off the adjective clause. If we take the adjective clause out, the sentence reads like this: “The man had a tattoo of a sailboat on his arm.” Grammatically, it is correct, but we are left wondering which man has a tattoo on his arm. Therefore, the information is essential, and no commas are used with the clause. If we use commas for the clause, the meaning will be different:

The man, who stole Bob’s luggage, had a tattoo of a sailboat on his arm.

The meaning of this sentence is that we already know who the man is and that he had a tattoo of a sailboat on his arm.

• To mark words of direct address.

Direct address shows that someone is being directly spoken to.

Examples: John, could you open the window?

Mary Jones, you have just won a new car!

• To mark the beginning of a direct quotation.

Example: Paul said, “I feel like my head is going to explode.”

• To separate items within a date.

Example: Hurricane Floyd hit New Jersey on Thursday, September 16, 1999.

· To separate items within an address, or to separate the name of a city from the name of a state or country. Also use the comma if the place is not the last item in a sentence.

Example: George works at Roger’s Diner, 400 First Avenue, San Francisco, CA 90028.

Example: Maria will be visiting Toronto, Canada, in May.

Example: Hershey, Pennsylvania, is a place where a lot of chocolate candy is made.

• To open or close an informal letter.

Example of an opening: Dear Rita,

Example of a closing: Very truly yours,

The Period (.)

• To mark the end of a statement, a weak command, or an indirect question.

Examples: I don’t play the piano. (Statement)

Turn off the lights. (Command)

I wonder where everyone is.

How do you know where the sentence ends? Every sentence except for commands, which have an understood “you” as the subject, must contain a subject and a verb. The sentence may or may not have an object.

Fragment	Complete Sentence
(Command)	Stop!
(Subject fragment.) My dog.	My dog always barks at the mail carrier.
(Verb fragment) Is a beautiful place.	Paris is a beautiful place.
(“To” fragment.) In addition to working at Tom’s Pizza.	In addition to working at Tom’s Pizza, Rita also sings at the Riverside Lounge.
(Adverb clause fragment) When Bob went to Hawaii.	When Bob went to Hawaii, he swam, surfed, and water-skied.
(Adjective clause fragment.) The man who played the piano at last night’s concert.	The man who played the piano at last night’s concert has played with the Boston Symphony Orchestra.
(Noun clause fragment) That he is a talented actor.	I believe that Dustin Hoffman is a talented actor.
(Gerund fragment) There are three things that Bob loves to do. Eating, sleeping, and water skiing.	There are three things that Bob loves to do: eating, sleeping, and water skiing.

The Semicolon (;)

· To join two closely related independent clauses that are not joined by a coordinating conjunction.

Example: The dog started barking loudly; the cat jumped on top of the refrigerator.

Without semicolon: The dog started barking loudly, so the cat jumped on top of the refrigerator.

· To join two closely related independent clauses and a transition.

Example: Nancy hates cold weather; therefore, she won’t go skiing.

· To separate items in a series that already contains commas.

Example: Flight 544 will stop in Newark, New Jersey; Miami, Florida; Dallas, Texas; and Los Angeles, California.

Other Sentence Problems

Fragments are not the only problems that a sentence can have. Two opposite problems are the comma

splice and the run-on sentence.

A comma splice is a sentence that has two or more independent clauses joined only by a comma.

Example: Hilary Rodham Clinton was the First Lady of the United States, she later became a senator.

The comma is too weak to join the two sentences together. Therefore, stronger punctuation is needed.

Comma splices can be fixed by:

(1) Separating the clauses with a period and capital letter.

Hilary Rodham Clinton was the First Lady of the United States. She later became a senator.

(2) Making one of the clauses dependent.

Hilary Rodham Clinton, who was the First Lady of the United States, later became a senator.

(One clause became an adjective clause.)

A run on sentence, which is also known as a fused sentence, is two or more independent clauses that are run together with no punctuation.

Run-on Example: The president has made an important decision few people agree with it.

Run-ons can be fixed by:

(1) Separating the clauses with a period and capital letter and using a transition.

The president has made an important decision. However, few people agree with it.

(2) Using a coordinating conjunction and a comma.

The president has made an important decision, but few people agree with it.

(3) Using a semicolon and a transition word.

The president has made an important decision; however, few people agree with it.

(4) Making one clause dependent.

The president has made an important decision although few people agree with it.

The president has made an important decision with which few people agree.

Written by the tutors and staff of the English Language Resource Center at Bergen Community College, NJ