Comma Placement
The comma was originally invented in order to avoid confusion in sentences; however, since it can be used in so many different ways, students are often confused as to when and where it should be placed. Many students have been taught, for example, that a comma should be placed wherever the reader pauses. The problem with this reasoning is that each reader might pause at a different place in the sentence.
This section is intended to provide some instruction on the basic grammar rules that determine when and where the comma is placed. These rules speak to the common errors that most students make when placing the comma. There are additional comma rules, but they are less troublesome for most students; therefore, they are not covered here.
The Six Most Commonly Misused Comma Rules
Rule #1
Place a comma after an introductory or transitional word.
Examples
However, it is necessary to write a lot of papers in college courses.
Therefore, it is useful to know where to place the
comma.
Rule #2
Place a comma after an introductory clause.
Examples
Given that he was unprepared for the test, he did perform well
on it.
At the end of the movie, we realized who the murderer was.
Rule #3
Place a comma after a dependent (or subordinate) clause.
Examples
Since it was raining, I brought an umbrella.
Because I didn't sleep well last night, I am tired today.
Rule #4
Place a comma before a coordinate conjunction in a compound sentence.
Examples
He was late getting to class, and the other students had already
begun the test.
She went to bed early, so she would not be tired the next day.
Rule #5
Place a comma to set off an appositive, an explanatory phrase after a noun.
Examples
Mrs. Smith, our next door neighbor, walks her dog every day.
Mr. Jones, the pharmacist at the drugstore, fills our prescriptions.
Rule #6
Place a comma before and after a parenthetical expression.
Examples
We can go to the party, I suppose, if we don't stay too late.
There is a lesson here, I think, for all of us.