Comma Usage

There are Four Basic Rules for comma usage:

1. Commas precede coordinating conjunctions when they link independent clauses.
2. Commas are needed after introductory words, phrases, and clauses that come before the main clause.
3. Commas are used to separate items in a series.
4. Commas are used to set off nonessential word groups or parenthetical clauses.

Rule # 1
Commas precede coordinating conjunctions when they link *independent clauses.
Example:
The minutes would pass, and then suddenly Einstein would stop pacing as his face relaxed into a gentle smile.
*An independent clause is a group of words with a subject and a verb that can or does stand alone as a sentence.
Independent Clause: The minutes would pass and
Independent Clause: then suddenly Einstein would                                  stop pacing . . .

Other Conjunctions:
                              but, or, for, nor, so, yet   

Common Errors:
If you use a comma without a conjunction you have a comma splice.
Incorrect: The minutes would pass, then suddenly Einstein would stop pacing… .

If you omit the comma and the conjunction you have a run-on sentence.
Incorrect: The minutes would pass then Einstein would stop pacing… .

Use a semicolon between independent clauses in a sentence when you are not using a conjunction..
Example:
The minutes would pass; then suddenly Einstein would stop pacing… .

Rule # 2
Commas are needed after introductory words, phrases, and clauses that come before the main clause.

Introductory words:
                           no, well, yes, however, first, in fact

Example: Well, perhaps he meant no harm. In fact, he wanted to help.

Introductory phrases are long prepositional phrases
(usually four words or more):
Example:
Due to his determination not to get a “C,” he did all his homework.

Introductory Phrases: with -ing verbals, -ed verbals, and to+ verbs :
Examples:
Having finished the test before the bell rang, he left the room.
Tired of never having enough money, she took a second job.
To get a seat close to the stage, you'd better come early.

Rule # 3
Commas are used to separate items in a series.
Example:
The movie was action packed, suspenseful, and romantic.
* The comma before “and” is preferred.

Words, phrases, and clauses in a series:
Example:
He spoke to Julio, then called his roommate, and finally phoned me.

Rule # 4
Commas are used to set off nonessential words groups (parenthetical clauses).
When a nonessential clause is removed, the meaning of the main clause is the same.
Example:
The restaurant, which only serves breakfast and lunch, was closed.

Word groups following nouns that identify or explain the nouns are nonessential and need commas.
Examples:
Uncle Ike, a doctor, smoked too much even though he warned his patients not to smoke.
She is a good friend, a person whom I trust and admire.

One Final Rule:
Commas occasionally may be needed for ease of reading, and clarity.
Example:
Still, water must be transported.

• REMEMBER:
  Be consistent when using commas.
  A comma's main purpose is to add clarity for the reader.
  When in doubt - don't.