1. to Separate Items in a Series. Example

CHAPTER 19-1

Comma usage

Commas are the most frequently overused punctuation remarks. Just remember that they are like road signs saying “Slow.” They tell the reader to slow down to avoid confusion. The simplest rule is this: If there’s no chance the reader will get confused without the comma, then leave it out. If the reader might get confused, then use it. If in doubt, omit it.

Do use a comma

1. To separate items in a series. Example:

The new dean enjoys sailing, cooking, stamp collecting and gardening. (Some stylebooks specify that a comma should be used before “and,” but the AP Stylebook omits this comma.)

2. After years or names of states or countries when they fall in the middle of a sentence. Examples:

He left school on May 3, 2012, when he finished the semester.

He went home to Fairbanks, Alaska, to take a summer job.

3. Between complete sentences separated by a conjunction. Example:

The fire alarm went off for the third time, so the motel clerk called the fire department.

4. To set off long introductory clauses and phrases from the rest of the sentence. Example:

When the fire alarm went off for the third time, the motel clerk called the fire department.

5. To set off parenthetical (nonrestrictive) clauses, phrases and modifiers from the rest of the sentence. (If the sentence makes sense without the clause, phrase or modifier, then set it off with commas.) Refer to the AP Stylebook for a complete explanation of punctuating restrictive and nonrestrictive clauses). Examples:

My two sisters, who are older than me, both live in Alaska.

The motel fire, which started around midnight, did not cause serious damage.

6. To set off appositive phrases (phrases that follow and explain a noun). Example:

John Smith, vice president for finance, said the company expects a shortfall.

7. To set off quotes (preceding or following the attribution “said”). Examples:

John Smith, vice president for finance, said, “The company expects a shortfall.”

“The company expects a shortfall,” said John Smith, vice president for finance.

8. If the absence of a pause might confuse the reader about what follows.

Don’t use a comma

1. To set off nonparenthetical (restrictive) clauses, phrases and modifiers from the rest of the sentence.(If the sentence doesn’t make sense without the clause, phrase or modifier, then don’t use commas.) Refer to the AP Stylebook for a complete explanation of punctuating restrictive and nonrestrictive clauses). Examples:

Two sisters who sought refuge in a church were injured when the tornado struck the building.

Two storage buildings that are owned by the Smith Farm were also damaged by the tornado.

2. To set off subordinate clauses and phrases placed at the end of the sentence. Example:

The motel clerk called the fire department when the fire alarm went off for the third time.

3. Before prepositional phrases (phrases beginning with “to,” “from,” “into,” etc. followed by a noun). Prepositional phrases never contain verbs. Example:

Wrong: The tornado slammed into the barn that sits, beside the house next to the hill.

4. Between compound verbs in a sentence with only one subject. Example:

The motel clerk called the fire department and started notifying guests about the fire.

5. Between two complete sentences without a conjunction. This creates a run-on sentence. Example:

Wrong: The fire alarm went off for the third time, the motel clerk called the fire department. (Use a semi-colon or period between the two sentences.)

6. To set off a month and a year without a date. Example:

He graduated from the university in May 2011 before enlisting for military service.

7. To precede a partial quotation. Example:

John Smith, vice president for finance, said the company expects “a shortfall.”

8. Before “Jr.” or “III” when it follows a name (according to the AP Stylebook—some other stylebooks say to use a comma before “Jr.” or “III”). Example:

Thomas Smith III.

9. When you should use a colon or dash to introduce an unexpected statement. Example:

The new president was in for a big surprise: the company was bankrupt.

10. If you don’t know a specific reason or rule to use it.

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