The comma is one of the most common punctuation marks -- and one of the most frequently misused! Here are some basic rules for using commas correctly:
1) In a series of nouns or phrases used with and, place a comma after each item that occurs before the word and.
Red, white, and blue
First, second, and third
first in war, first in peace, and last in the American League
(Note: Some style manuals call for no comma before and in such a series. If your office uses one that does, follow that style.)
2) Use commas to set off parenthetical information.
Barry Bonds, who plays for the San Francisco Giants, is the current home-run leader.
The symphony, which started out serenely, ended with loud music and bursts of cannon fire.
3) Use a comma to join clauses before and, or, and but if the clause following forms a complete sentence. Generally omit a comma if the phrase following does not form a complete sentence.
The tsar was supreme commander of the Russian forces, but he had difficulty getting generals to follow his orders.
The president is elected for four years, and he can run for a second four-year term.
Members of the House of Representatives are elected for two-year terms and have no term limits.
Senators used to be elected by state legislatures but are now elected by the people of each state.
4) Never use a comma to separate the subject from the verb or to separate a modifier from the word it modifies:
Wrong: Dealing with rain seven days in a row, has been difficult. Right: Dealing with rain seven days in a row has been difficult.
Wrong: It was a dark, stormy, scary, night. Right: It was a dark, stormy, scary night.
Commas in dates:
1) Use commas after the day of the month in a complete date when the date is in month-day-year format:
July 4, 1776 Sept. 11, 2001
But note that military-style dates in the day-month-year format are written without commas:
23 October 1986
2) Don't use a comma when just the month and day or month and year are given:
In July 1776 the Continental Congress agreed on the Declaration of Independence. In July 1863 Union forces won key battles at Gettysburg, Pa., and Vicksburg, Miss. She was born on March 29 in Galveston.
3) When a complete date is given in a sentence, put a comma after the year as well as after the day:
Dec. 7, 1941, and Sept. 11, 2001, are tragic days in American history. The first day of the new millennium was Jan. 1, 2001, not Jan. 1, 2000.
4) When you use the day of the week and the calendar date, place a comma after the day of the week: