Comma Rules to Live By

These pesky little punctuation marks serve to give us pause, which leads to clarity in our sentences. To help you, keep these rules in mind:

1. Use commas to separate series, but know whether that series is simple or complex.

Simple: He bought books, paper and pencil before school started. (No comma before and.)

Complex: He knew that the township needed more roads, parks and recreational facilities, and sewage line access to increase development. (Comma before the final and because the series has two ands in it.)

2. Introductory clauses need to be separated from the main clause with a comma.
In only 20 days, she had transformed the college.

3. Direct address, which is usually a noun or the words yes and no that relate to but are not part of the sentence's main clause, needs a comma after it.
Yes, the Steelers will be in contention for the Super Bowl again next year, Cowher said.

4. Nonrestrictive clauses and phrases, which add extra information to sentences, need to be set off by commas. They usually (but not always) start with which or who.
The game, which had been scheduled six months ago, ended in a tie and had to go into overtime.

5. Appositives, phrases which precede or follow a noun and describe it, require commas.
John Johnson, the chairman of the committee, has resigned.
The team's pitcher, Sam Bradley, has only won two games in 10 starts.

6. Participial clauses and phrases, which modify some part of the main or independent clause, must be separated by commas.

The Senate adjourned today, having completed all its business.
Singing in unison, the protesters circled the building and wouldn't let the workers enter the plant.

7. Two independent clauses joined by a conjunction need a comma as a pause.
Seven men were arrested this morning, and police vowed to find five more they say are involved in the operation.

8. Commas separate two modifiers of equal weight that describe a noun.
Meteorologists forecast another cold, dreary night in Pittsburgh.

9. Parenthetical expressions, which are similar to theatrical asides, require commas because they are transitions and lead into the main clause.
Some council members, you may recall, didn't want to appropriate the extra money for two new parks until residents demanded it.

10. Dependent clauses require commas to be set off from the main clause. A good example of this is attribution.
The study, researchers claim, will change the way drugs are administered to AIDS patients.

Watch out for these common comma errors:

The sentence started with an introductory clause, she couldn't tell what it was.

This is a comma splice. The two clauses are independent and can be fixed by adding a conjunction (such as but), changing the comma to a semicolon and making it two sentences.

The mayor decided to visit the residents, because she needed their votes.
Because is a conjunction that introduces a dependent clause. When because is in the middle of the sentence, no comma.

Bryant, himself, will deliver the package to the shareholders.
Himself is a reflexive or "self ' pronouns used to intensify or accent the noun it precedes. No commas around it.

The candidate charged his opponent was, "a fake and a charlatan."
Don't use a comma to set off a partial quotation.

Firefighters found, on the steps, two crying children and led them out of the building.
Prepositional phrases do not require commas the majority of the time. One exception is if it is an introductory phrase into the main clause of the sentence.

He worked hard for his money, and spent it like water.
Don't put a comma before every conjunction you see, particularly and.
What follows here is a phrase. Always look to see if the words that follow a conjunction can stand on their own as a simple sentence.