Lesson 5: Comma use.
Commas are your friend. Use them wisely.
Use commas to separate independent clauses when they are joined by any of these seven coordinating conjunctions: and, but, for, or, nor, so, yet. EG:
The game was over, but the crowd refused to leave.
The student explained her question, yet the instructor still didn't seem to understand.
Yesterday was her brother's birthday, so she took him out to dinner.
Use commas after introductory clauses, phrases, or words that come before the main clause. EG:
While I was eating, the cat scratched at the door.
Because her alarm clock was broken, she was late for class.
If you are ill, you ought to see a doctor.
When the snow stops falling, we'll shovel the driveway.
Common introductory phrases that should be followed by a comma include participial and infinitive phrases, absolute phrases, nonessential appositive phrases, and long prepositional phrases (over four words). EG:
Having finished the test, he left the room.
To get a seat, you'd better come early.
After the test but before lunch, I went jogging.
The sun radiating intense heat, we sought shelter in the cafe.
Common introductory words that should be followed by a comma include yes, however, well.
Use a pair of commas in the middle of a sentence to set off clauses, phrases, and words that are not essential to the meaning of the sentence. Use one comma before to indicate the beginning of the pause and one at the end to indicate the end of the pause.
Use commas to separate two or more coordinate adjectives that describe the sa me noun.
Use a comma near the end of a sentence to separate contrasted coordinate elements or to indicate a distinct pause or shift. EG:
He was merely ignorant, not stupid.
The chimpanzee seemed reflective, almost human.
You're one of the senator's close friends, aren't you?
The speaker seemed innocent, even gullible.
Use commas to set off phrases at the end of the sentence that refer back to the beginning or middle of the sentence. Such phrases are free modifiers that can be placed anywhere in the sentence without causing confusion. (If the placement of the modifier causes confusion, then it is not "free" and must remain "bound" to the word it modifies.)
Use commas to set off all geographical names, items in dates (except the month and day), addresses (except the street number and name), and titles in names.
SO IMPORTANT: Use a comma to shift between the main discourse and a quotation. EG:
John said without emotion, "I'll see you tomorrow."
"I was able," she answered, "to complete the assignment."
In 1848, Marx wrote, "Workers of the world, unite!"
Use commas wherever necessary to prevent possible confusion or misreading.
When not to use commas:
Don't use a comma to separate the subject from the verb. EG:
An eighteen-year old in California, is now considered an adult. (in correct)
The most important attribute of a ball player, is quick reflex actions. (incorrect)
Don't put a comma between the two verbs or verb phrases in a compound predicate. EG:
We laid out our music and snacks, and began to study. (incorrect)
I turned the corner, and ran smack into a patrol car. (incorrect)
Don't put a comma between the two nouns, noun phrases, or noun clauses in a compound subject or compound object. EG:
She was late for class, because her alarm clock was broken. (incorrect)
The cat scratched at the door, while I was eating. (incorrect)
All info taken from here.