Tips for Using Commas

First, some comma "rules" that aren't rules at all:

• You may have been told that you should always use a comma before "and" and "because," but this is not true. If the "and" or "because" in question fits into one of the rules listed below, then you should include the comma. If not, the comma is not needed.
  
• You may also have been told that you should insert a comma whenever there is a slight pause in the sentence when it is read aloud (i.e., whenever you "breathe"). This method sometimes works, but it can also create problems. Sometimes we take breaths in a longer sentence, even when no comma is necessary. Sometimes we rush through other sentences without taking a breath, even in places where a comma is needed. Try using the following rules to decide whether commas are needed in your sentences.

The following comma "rules" are actually guidelines that allow you, as a writer, to test your comma use based on meaning. In several of the cases below, the decision of whether to include or to omit the comma actually alters the meaning of the sentence. Before you can make your final punctuation decision, you need to be certain about what you are trying to say.

Commas are used to set off introductory material (such as a word, phrase or clause) before the subject of a sentence.

• Training six days a week, Marianne prepared for the Olympics.
  
• Because she was both talented and dedicated, she made the U.S. Fencing Team.
  
• In the summer of 2004, she will travel to Athens for her Olympic debut.
  
• Actually, she is more interested in making new friends than in winning her event.
  

Commas are used to separate three or more items in a list. If there is an "and" or an "or" at the end of the list, we usually include a comma before it.

• John asked his sister to go to the supermarket and buy bread, milk, and eggs .
  
• He needed these ingredients in order to fix French toast for breakfast, to make some peanut butter and jelly sandwiches for lunch, and to bake a chocolate truffle cake for dessert .
  
• When John's sister returned, he had to decide what to make first: the French toast, the sandwiches, or the cake .

Commas are needed to set off words, phrases, or clauses that are inserted as additional information at any position in a sentence, but only when readers don't need this information to understand the overall meaning of the sentence. The comma signals the reader that the information is helpful to understand your overall argument, but not to understand the sentence itself. You can think of these commas (or a comma and period, as in the final example below) as a set of handles: they let you lift the enclosed words and phrases out of the sentence without changing the sentence's basic meaning.

• Russell Conwell , who founded Temple University in 1884, wrote a famous sermon called "Acres of Diamonds."
  
• Russell Conwell , the founder of Temple University, gave his "Acres of Diamonds" speech over 6000 times.
  
• Today's Temple students , however, often disagree with Conwell's argument.
  
• The "Acres of Diamonds" speech is used in many composition classes , even though students often disagree with Conwell's argument.

Commas are used to indicate dialogue or to set off a quotation with some identifying material. However, if your introduction to a quotation uses the word "that" or involves a partial sentence incorporated into your own sentence, you do not need to include a comma.

• Peter said , "Are you going to dinner tonight?"
  
• "I'm not really hungry ," replied Joni.
  
• Conwell states, "It is all wrong to be poor, anyhow" (65).

But:

• Conwell states that "it is all wrong to be poor, anyhow" (65).
  
• A conditional gift is one that "may be stated in specific words or it may be inferred from the circumstances"
  
• Clement Scott claimed that "the vision of Ophelia does not suggest to Hamlet passion, but purity" (47); the performance suggested that Hamlet was exhorting Ophelia to "save [her]self from the contact and contamination of man while [she] can!" (Scott 47).

Commas are needed to separate complete sentences joined by one of the seven connecting words (for, and, nor, but, or, yet, so). The comma must come before the connecting word.

• Many people would agree that Conwell has a small number of valid points in his speech , but the majority of his speech was completely nonsense.
  
• Americans depended on air power , and we were weak in close hand to hand combat.